Sadly reminds me of my mom's dog. Through a total lack of exercise and constantly feeding him human food, he was full blown diabetic by like 7. Get a call one day that she needs my help getting him to the vet. He's laying on the floor, panting and sweating and can't get up. I have to dead lift a 70 pound dog multiple times myself to get him into the car and into the vet. Vet says he's in late stages of diabetic shock and we have to put him down.
This is after I made it a point to exercise him multiple times a week when my mom was in the hospital and I had to take care of her everything for her for months.
That shit sucks man, I'm sorry. But you should accept that putting them down is the only financially reasonable, and more importantly, humane solution. If a test for parasites isn't too expensive I would still go for that to see if they just have a bad parasitic infection though.
I took my Dog to get her put to sleep... that's probably the hardest I've cried in years. The people at the pound surmised that she had an infected uterus (I was wrong about it being anal bleeding...), and an emergency spay could fix it, but that would be a ruinous 1000+ dollar operation that's not even guaranteed to work... I really feel like I failed her, but I don't know what I could have done. I feel it's my Mom's fault for not getting her spayed (I thought she was...) but it's too late to assign blame.
Ultimate it's for the best, my Mom was too old and frail to be taking care of a big dog (her paw claws were seriously overgrown, a sure sign that she wasn't getting any exercise) and my Sister could not care about anything whatsoever. I can't take in any animal in my apartment... It seems this was just her fate. I just hope she knew I loved her.
Thanks Nenjin and Dragdeler, I appreciate the advice and support that can be found here.