My suggestions would be first of all, to not charge your arrows, they're better combined with short hops to keep your opponent off balance, so to speak, when you charge them it makes you somewhat predictable. Also don't overcommit to your attacks, try to fake your opponent out more, and as Link, one thing that should be more or less automatic is keeping your projectiles on the field at all times. Bombs in the air and boomerangs constantly flying around the level will make your opponent less happy.
As far as your close-range combat, just let yourself pretend that you're in a sudden death match and you have to hit your opponent without letting them hit you. That strategy may sound overly simple, but just give it a whirl and I guarantee it'll help.