This is a very interesting dream, I would like to hear more about this symbol you saw in the room. There are many things that could have significance in this dream and the fact that you were sharing this dream with your friend could simply be because you are close and are leaning on eachother in this time of transition. As for interpretation help, I don't know what help I can be, but I can try.
Starting from a background perspective: the subconscious is a crazy place. Many believe that it is our connection to the etheric plane or even the akashic field (the unification of everything and anything basically), but the main bit is that dreams are the subconscious' way of telling us something that we would otherwise never know or trying to warn us. Our subconscious uses symbols and concepts that we are likely to figure out. The important thing to remember is exactly what you were feeling while you had this dream. This could be relevant or it could be a reflection of your deeper psychological state. You will need to sort out what is related to the dream and what is overflow from conscious life. First impressions are everything, even in the dream world. If you know something then it is probably true.
Down to the bits: The room you are describing sounds ancient and like it is part of something that has long since been forgotten. I would venture to guess that it has a ritualistic significance for this ancient feeling culture. I would be willing to bet that this man you saw was a part of that culture and is trying to reach out to you. Having looked at some of your past posts, I would also venture to guess that he is not the only one who is reaching out. It sounds like the woman from your "white buffalo" dream may be trying to reach out to you, but in a different way. I would also feel like they are related or connected in some way. The woman from your other dream was testing you and observing you, and it sounds like she was happy with what she saw. This man seems to be her counterpart that wants to reach out to you. The fear that you felt could be misinterpreted. New things are often seen with apprehension and fear. This is a new chapter in your life and someone or something sees some potential in you. You have power in you that is being noticed. The fact that you switched your dream is evidence enough. It would seem that the zannia was the man's attempt at bringing you back to the first dream. Sometimes when you enter a new chapter in your life, it feels as though it is the death of the last bit. Also the fact that your friend saw you in relation to when the man was either with you or trying to bring you back is interesting. Your friend was appearing as a component; as someone who is only part of the background and not the action of the dream. I believe this would have meaning in and of itself, but would require more information to come to a proper conclusion.
Summation, here's what I think: It would seem that there are hidden symbols within a larger picture. Omens or gems of concept. I feel that the "white buffalo" dream and this dream are connected, and that there may be more that you haven't mentioned here. It would seem that since you have turned down this path and opened yourself up to a new world, that someone (or something) has taken notice of you and wants you to be a part of whatever they are. I get the impression that the woman in your first dream was trying to test you and you somehow passed her test. This got the attention of a group at large and the man was dispatched to try to reach out to you. I think the fear you are feeling is apprehension rather than actual fear. You have made the choice to walk down a different path than your family has, and whatever untapped talents that they possessed has been passed to you. The difference is that this power within you is being noticed BECAUSE of the path you chose. I would guess (as pure axiom) that your family is not only NOT Wiccan, but might hold an opposition to the path. This is where your apprehension and fear is coming from. We are the product of our environment whether we like it or not. Apprehension is a good thing. Curiosity killed the cat because the cat doesn't have enough apprehension or fear to recognize the danger until it is too late. You have a good head on your shoulders and know the difference between good and evil. I believe you will do what is right when the time comes. With regard to your friend's involvement, I think that she is only there because YOU are there. Whatever this is is not after her, but just you. She is still there and able to see you because she is attached to you. You are both walking this path together and have a bond that cannot be broken so easily. She will be a component in whatever is to come, but not involved. It shows you that she is there for you and is a part of you in a sense. Whatever this is has made it clear that it doesn't want her, but understands it can't just get rid of her because to do so would hinder your progress. I would venture to guess (again pure axiom) that you are the dominant one in your relationship with your friend whether obviously or not or consciously or not.
Symbology as I see it: Starting from the beginning (by that I mean the "white buffalo" dream), I would say that there are a few symbols here that I don't understand but they still stand out. In the context that this dream was a test, I can draw a few conclusions. Firstly that the feather and your grandparents are symbolic of what you are willing to give up or sacrifice in the discovery of your new path and journey. It would reflect to the woman that you are not willing to sacrifice nature or the innocent, but you know that you must leave some aspects of your family behind you in your path. I would guess that your grandparents (whom you have never met) would have been very intuitive as to what you are doing and might not have been so supportive. Therefore they are the symbol of the aspects in your family that you will have to sacrifice on your journey. This dream also shows that you are willing to take risks and show bravery, but you have a strong enough will not to allow your life to be taken by force. You will maintain control over your life while allowing your environment to fluctuate and nature to take its course (maybe even help it to grow and return to a former beauty). As for the test in the lake with the gun, I might say that it shows you are willing to take instruction and learn within a group. As for your friend's sister, I would wonder if she hasn't considered a similar path as you, and you will eventual nurture her along and help her to understand (take her under your wing of sorts). On to the current dream. I think the biggest symbols would be the flower, the water, and the fire. The water would represent the friendship you have with this friend. If it were to be empty, then you would be lost without her and she would no longer be in your life. This group that wants you doesn't want her, but knows that she comes with the package. This is where the fire comes in. Fire is often seen as an obstacle or wall. This man is using the fire as a way to keep your friend at bay while not discarding her and separating her from you. Fire may be an obstacle, but it is not insurmountable. He chose this to show you that he doesn't want her, but is not trying to get rid of her. The flower is a way of connecting you to your friend. It was offered to you to show that you do not have to forsake her, but that she may not be involved in everything you will. It appeared in the water because that is the epitome of your friendship. When you picked it up and kissed it, you were accepting the connection and acknowledging that there may be times of distance and separation, but that you will never forsake your friendship and will always be there for her. It sunk down to her so that she would know that you have accepted this and she is being told about it. She was only in your dream this time to let her know the aspects that pertain to her. You won't ever forsake her and you will always be there even though she may not be with you or involved in what you are.
All in all, this doesn't seem to be a bad thing. It would seem that if you choose to accept whatever this offer is, then you will be at it alone in a physical sense, but you will still have your friend. She just won't be able to join you on this journey. Whoever this is that is extending a hand is accepting and understanding. They seem to value the positive attributes in you. The may seem stern or course, but they are good at heart. This is not something that is so cut and dry as far as good and evil, but is more of a way to learn and what you take from it is on you. They will teach you, but how you use it is up to you. They would clearly prefer someone who is good and pure at heart such as yourself, but they know that there are always aspects of evil inside everyone and we still have free will.
That is how I see your dream. I'm sorry, but the more I wrote, the easier it was to see more than what was there. You have a good heart and will do what's right. You will know when to say no. You have a strength in you that may be untapped and just needs the right trigger to be exposed. There is a lot of very personal aspects to these two dreams that reveals quite a lot about your deepest self. Bear in mind that this is entirely my opinion. If there is something that doesn't feel right or fit, then perhaps I'm off. I don't know you personally so I can only be so accurate. Being empathic certainly does help though.
May the Gods be with you, and the hand of Fate be a gentle touch to guide you.