Well a possible bit of relief is that the warmer the water, the harder the fish has to work to get O2
out, so seems to me because of the way the gills process the water they have to breathe more for the same O2
Do you have anything circulating tje water?
You can clean the sponge filter gently, with declorinated water as a start.
I think circulating more water may help. I'm not sure what it is specifically. It's too hard to see the pics detail.
Check what freshwater sponges look like. See if they might look the same.
Do the stringy things wiggle like worms in the water, check Planaria, and Planaria swimming.
Maybe someone else can tell.
Happy to hear your fish is doing much better!!!
I had one Betta fish which required the ES for the rest of it's life at 1 teaspoon per gallon. But he lived in his own 5G container and probably lived another year.