Try feeding him a shelled pea. If you have frozen peas, take one, microwave it in water to thaw it out and pop it out of its shell.
Swim bladder issues can be from multiple sources, one of which is poor water conditions. Whether it is swim bladder or ammonia poisoning, or something similar, the treatment is still going to be lots of clean water and a good diet.
EDIT: The red gills can be a sign of ammonia poisoning. However, its hard to tell sometimes with bettas what is their normal color and what isn't.