Yesterday turned out better than I expected. The cat's surgery was a great success, though unbeknownst to me, putting it off for two short weeks meant that the problem got worse, and while he wasn't apparently feeling any pain two weeks ago, it was clear to the vet that he had an exposed nerve in his mouth and was in horrible pain. I had no idea - he wasn't showing any indication of being in pain. The lesson here is to not put off surgery for a pet, no matter the cost.
And on the money note, the estimate they gave me was a high estimate, one that would cover after care antibiotics and pain pills. He didn't need either, since he had no infection and the dull ache he would feel after surgery was nothing compared to the exposed nerve. Even with picking up some prescription food for the other cat ($50 for one 17 lb bag!) the cost was still significantly lower than what I was quoted. I can't complain.
So all in all, yesterday was a great success. I'm going to continue to build up my pet fund so that I'm ready for any additional unexpected expenses that might come my way. And perhaps I'm going to build a cat treadmill to help the fat one lose some weight so I don't have to keep buying $50 food for him. We've tried all the traditional routes (non-prescription weight-loss cat food, exercise, limiting his food, etc) and he continues to gain weight. Clearly a gym membership is the next step.