Is it both sides or just one side? Dropsy would have already killed him by this point, his scales would raise and his entire body would bloat up, not just one side and then he'd be quickly gone so no, it's not Dropsy. which is a good thing!
And looking back now, he doesn't look any more swollen from his first pictures. His fins do look better though so that's a good sign
But there won't be much else you can do for him except keep up the Epsom and water changes for him to be comfortable unless you can find a Vet who can remove it from him but that's going to be super costly and very risky :-/