Poor Max, I hope he isn`t in too much discomfort. I think you are right to be a bit worried about his stomach being swollen, you never know what he has in there! Gastric torsion is the same as Bloat right? I don`t know much about it but I think that it is if he is not passing the gas he is in trouble. Please don`t take my word for it though, like I said, I know very little about it. Anyway, I found bloat at the Pet Symptom Solver site and that may help, here is the link if you want to check it out.
http://www.ivillage.com/pets/petsymp...437741,00.html

Sure hope there is nothing seriously wrong. Will be keeping him, and you, in my thoughts.

Chris