You're on the right track with thinking about the rudder. Ideally you'll keep the wings "level" around the loop with aileron and correct any in/out using the rudder. Rudder works opposite (cringe) when you're upside down in the same way ailerons work opposite when you're flying towards yourself, some people use tricks to remember which way to push things other people just learn to push them the right way without having to think about it. Either way, wrong rudder shows up real quick to you and the judges :-)

You're also pretty close on that if your plane is banked with the outside wing low and it's pulling positive G at the top it will turn towards you a bit, but if it's slowed down and generating negative G it'll turn away from you a bit.

Keeping the airspeed up and tightening the loop helps by keeping the plane less at the mercy of wind gusts and engine thrust issues at the top with high power and little airspeed.

The key is, find a size that your plane/power combination is happy to fly at and stick to that size. A bigger loop will (but shouldn't) score higher than a smaller loop but a big wobbly loop won't score as well as a smaller round loop will..