I would suggest asking your vet to try 10-14 days of Baytril
There are many different methods of figuring out what is painful to animals. A ton of research has gone into the AVMA's humane euthanasia recommendations.
I'm confused how any human, vet or not can tell us what is painful to an animal. and leos aren't like dogs they dont make sounds in pain. take it as if it were your self how does it feel when you cant breathe let alone in a zip lock bag in a fridge or freezer...thats just mean and unethical to me IMO. but to everyone their own. ill go rob a bank if i got to make sure i can go to the vet and make sure my suffering animal gets an injection to put it down quickly.