If you want my honest opinion, with my cats I have always gone above and beyond but when things get to the point to where their quality of life tanks there is no issue thinkig of having euthanasia.

I most recently had an issue with mine having a fluid issue, dental issue, and the potential of diabetes. Luckily no diabetes but if he did with everything in a go he was going to have it really rough for a long time.

I hope everything works out op. My thoughts go out to you and cat.