Just stop feeding him. They can go on for awhile without food so it's fine for a few days. Keep his water clean, and add the same meds you did when he had dropsy and he should get better....this fish is like a betta miracle!!
I never kill fish. I don't have the heart too. I'm one of the few breeders who dosen't kill perfectly good fish just because they're not great quality.
Depends. Breeders who are spawned several times die sooner than fish that don't spawn. But in general life span depens on care. A betta in filtered and heated tank will last longer than one in a bowl. If you excersize your bettas (gently chasing him around with a net) he'll get the excersize he needs and some live up to 10 years that way!!!