Sometimes you just can't cure swim bladder disease. If he refuses to eat the treatment and you really want this fish to survive, you may try force feeding him an epsom salt solution with a plastic syringe. There is an article with detailed instructions and dosage somewhere on this forum, I think it was posted by RD. Be aware that this is a very stressful procedure for your fish and it might not end well, but it's a good "last resort" method when nothing else seems to work.
Alternatively you can try force feeding him a food soaked in a broad-spectrum antibiotic since they are way more effective when ingested, and swim bladder disease might also be caused by parasitic/bacterial infections.
If the fish looks too sick, miserable and is swimming erratically all the time, you should consider euthanizing it.
