My cat is very sick. What else can I do?

My cat Grae (who is my baby) is about 14 years old. Until about 5months ago he acted like a young cat. He had a surgery to remove bladder stones and has been sick ever since. He first had pancreatitis, that was awful. This became a little better and it is stabilized with pancreatic enzyme pills daily. He has had hyperthyroid for years and it was fine, now it keeps getting worse and his tapazole dosage is much higher. He now has kidney stones, irritable bowel syndrome and feline hepatitis. He is super skinny, urinates all of the time and is super hungry. The vet says that there is not much we can do but try to make him comfortable. He is on a high dosage of Prednisone, Tapazole, Raglen (for vomiting) and pancreatic enzymes. Has anyone else experienced this? What else could I do for him? He was tested for lymphoma and was negative. Bladder cancer was not ruled out by biopsy yet, but vet doesn't think I should get that tested.