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!!
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!!!