swollen area near a clamped fin with a small white protrusion... That could be bacterial (with the white bit being dead flesh) or it could be an anchor worm - but you'd probably see more of them, and they'd have responded to the praziquantel, it could also be a fungus, but it would more than likely have spread to more of the fish by now. It could also be cancer...
I've had dwarf gouramis develop spot pattern bacterial infections that eventually ate through them and killed them, no matter what I did. Hopefully you don't have what they had.
I would suggest, since the infection has not responded to the praziquantel, that you do a nice, big water change and let him sit for a day and observe the white spot.
If it starts wiggling around, you know you have a parasite. If it's obviously a part of the skin itself, you know you have a skin infection that's possibly bacterial.
The fish is probably in distress at the moment, and I would attempt to soothe his pain with 1tblspoon of aquarium salt per 10 gallons of water (added slowly over a period of several hours). It should help balance out his fluids, and hopefully reduce any swelling at least a little.
However, it's difficult to medicate without knowing what he is sick with, first. Take some time with a good light and a camera, see if you can get a good look at it yourself and also try to get a photo so we can see what's going on. Also look up on the internet images of anchor worms and bacterial infections on the body and other such things, and compare with what you have on your fish. I've found a Google Image search to be INVALUABLE to attempting to diagnose problems with my fish.