do you have a spare tank that you can put him in? If you do, lower the water in that tank to double of his body size, up the temp to about 82f, add some salt, blackwater extract if you have and turn the lights off. He might be getting a swim bladder problem if he can't seem to keep afloat properly.
The jar that i took away had that problem, and took 2 months to get him 95% better.
I had him in a quarantine tank, added melafix, epsom salt, cranked the temp up to 84F for about 2 months. Also did w/c everyday, about 5-10% just to maintain clean water parameters. All I had in there was a sponge filter for the first month, and added in mini w/d into the 10g tank and in the last month I raised the water up to normal levels.
Another thing I did for about a week was to cover all sides of that tank and left about 1" view above the water level to force him to come up and look out since I kept the tank light off.
Dunno if this will help you out, but looking at the video again, his tail is drooping, and gasping for air at the surface, also that he's having a hard time now staying straight seems to me, a swim bladder problem.