First of all, I am deeply sorry for everything that is going on with your fur child. Both of my girls were really sick for a while and we almost lost them- it is truly heartbreaking and exhausting and I will remember you in my prayers tonight.
As far as a spell/ritual, when we discovered my dog's cancer I wrote my dog a letter in a simple communication ritual. I lit candles and wrote to her about what was going on as if I were speaking to a small child. I told her that she was sick, but we are working with doctors to make her all better. We reminded her that she might feel scared sometimes, but her doctors and her mom and dad were going to be with her 100%, every step of the way. Above all else, I told her that we loved her more than she would ever know. I gave all my energy to the letter and left it in her dog bed overnight, then burned it in the morning.
To me, it helped to assure her (and myself) that we were doing everything we can to make sure that she is going to be okay and that she is loved. When we were feeling uneasy, knowing that we did what we could to communicate nothing but love and reassurance to our girl helped to settle our nerves. Plus, I swear it worked... She walked into surgeries, chemo treatments, x-rays, and so on with confidence and was a happy pup throughout it all. For a dog with a severe anxiety disorder, it was pretty incredible.
I truly hope you find some sort of comfort in this stressful time. If you need to vent to someone, feel free to reach out to me. I am the crazy pet lady, I get these things completely.
A yawn is a silent scream for coffee.
Feel free to pm me if you have any questions! I am here to help.