Is he eating? If so, what?
What was his state before you brought him home....and the state of his tank and surrounding tanks there?
Can you get him out to at least do a freshwater dip? I know you made the best decision you could in the pinch and I agree it was a fine decision, but ideally you might've had a freshwater dip ready before you got the bag since you knew fish were coming. I float a shoe-box sized rubbermaid container that's full enough of
dechlorinated tap water to cover the target fish for at least long enough to match the tank's temperature....but longer as needed, like if you're expecting fish later.
Even though it's after the fact, I'd still try to net him out for a dip
if you can do it with minimal stress to him and the rest of the tank. Causing a lot of stress in the process may be worse than just letting it work itself out....for one thing the fish might be more susceptible to internal damage in this state, so tons of thrashing around the tank might not be ideal in and of itself.
Thankfully that bulge is not a sign of ich or velvet, so you should relax at least a little bit knowing that. The swimming into the powerhead is definitely concerning though as it implies trouble breathing.
Was he dry, out of water for any length of time? Was there any struggle with the cut-bag incident where he might've sustained injury? Was he ever in too warm or too cold of water?
