Hmm.
Well, it still could be dropsy - and the pineconing just hasn't started yet. Or it could be an internal infection. OR he could be constipated. Have you tried fasting him? Go 2 - 3 days without feeding, and in the meantime head over to the grocery store and get a bag of frozen peas. Cook some of them up for him in a microwave safe dish in dechlorinated water - then when they're done cooking, shell them and chop them up. Give him a few little hunks of it. It could be that he has a few things going on in there - and with the temp of the water what it is, that could be making things progress.
He could have some sort of internal infection which is messing with his organs, and therefore could affect his swim bladder eventually too.
If your fish were mine, I would not feed him for the next 3 days, give him some peas each day, once a day. If, after 2 days his belly hasn't significantly gone down, I would medicate him - get some Maracyn 2 (if you can find some). If he does have the start of dropsy OR some sort of infection going on in there, that will take care of both of those. M2 can be found at any lfs or at PetSmart or PetCo.
Is there any way you can try to bring down the temp of his tank easily?