Emily, sometimes we want to save animals despite their pain and suffering. I have worked as a volunteer alongside many people who run shelters and they have all said that no kill ideals can actually harm many animals that we keep alive and subject to poor shelter conditions when there is no hope they will be adopted or little hope they will be adopted.

It puts a huge drain on the shelter system to care for these animals and make decisions about who to treat and who not to treat. If your cat is having so many medical problems and so many vet visits are necessary, which you know are traumatizing for the cat, I dont think you'd be a bad person for helping him pass away and easing his pain. It sounds like he's in a lot of turmoil anyhow. No kill shelters do put down animals that are too sick to help. You would likely be just passing that stress onto them.

It's very hard to know when to help out furry friends pass, but just remember that it will happen sooner or later and you just have to try and do your best by him. From your description he sounds quite miserable and also like medical interventions are making him worse. In the case of a psychological problem with an older pet, sometimes the kindest thing is to help end their suffering. I have unfortunately had to do this and it sucks but I also felt it was the right thing to do.