On hang 5's the biggest thing to me is to not look down at the wheel. Look where you want to go or at least ahead of the tire.
The other thing is to sort of lock in between the seat, peg and bars like you, the bars/forks and the frame are a single triangular unit. Not like you're pressing hard against all three points, but enough that it doesn't wobble everywhere.
When you're in the balance point good, your leg just pivots at the hip, knee relaxed and you barely use your arms for balance at all. Your arms and hips are mostly for steering and massive corrections when you're getting all sketchy about to fall. For the most point, your fingers aren't used until you're doing circles so don't clamp the bars so tight either, just rest on them.
If you're bending your knee, you're really just flailing because it doesn't move your weight forward or back enough to do anything. Up isn't helping, think slightly back and way back.
It's also good to think of it as a pendulum. If you bend a pendulum, half the bend goes forward and half back so you just split the weight and raised the balance point. The radius of the pendulum is also shorter, so your balance point isn't as wide. It's like walking a tightrope with a stick half as long.
If your leg is going forward, you're not committed enough. It will be slightly back at the balance point and that point is a lot wider than you think once you get up there and have the confidence to feel it out.