Euthanasia

Hello! This post is hard to make, but I need opinions. We adopted a 18 year old deaf, blind chihuahua with a grade 5 heart murmur, his body was beat up pretty badly too, crooked neck that he can’t raise up, bent left back legs that is non weight bearing and and crooked/broken tail. They gave him two months to live, and we were okay with that and wanted to give him the best rest of his life we could. Well fast forward to 8 months later, he’s still here! :) problem is, I noticed he having trouble breathing, becoming more and more Incontinent, he sleeps a lot, he’s has horrible arthritis, he’s in gabapentin for his pain. But I don’t think it’s helping, he’s uncomfortable, moves a lot, can’t get comfortable. :( I think it’s time to put him down, but he still loves his food and drinks water okay. I know he’s in pain and I don’t want that for him. What do I do? What do people think ? I’ve had plenty and plenty of animals growing up that I had to put down but the signs were a lot more obvious like not wanting to eat, can’t walk no more. Etc. please be kind.. this is very hard for me. Thank you.

Update: We put him down this evening. 😭💔 rest in peace little guy. We gave him a really good meal and lots of love. He’s now with my other babies that have passed. Thank you everyone.