Big hugs and a hi from us as well!.
I agree with everything in this well advised response.You are doing a fantastic job of managing so many conditions for your girl!
Some thoughts about various issues:
Being hypothyroid is miserable. I tell you this from living it myself, so I would consider adding back a thyroid med.
The loose stools could be caused by sensitivity to wheat gluten (in humans this is often caused by celiac disease, which also occurs in some animals). Since you have to move to a low-protein diet for the kidney disease, maybe a food that is based on rice would work? Somewhere I have a recipe for making your own low-protein dog food and I know it's based on rice. I'm sure I can find it if you need it.
Except for the cancer, a lot of what you describe sounds like some form of autoimmune disease. Hypothyroidism and gluten intolerance are both in that category. Probiotics are helpful, so that's a good start.
And you'll hear from a lot of other people who know a lot more about these conditions than I do.
Holding you and your sweetheart in my thoughts and prayers,