1. I would assume from reading that rules that you can, but with movement from only one die available, you'll be lucky to even pass a single bike (except the one you may have just won the 'braking duel' with). I don't understand why one would get to ignore overtaking penalites, I think I would change that to apply overtaking penalties into the turn.
2. I thin Brian's answer is correct.
Can there only be contact in a curve (because the bikes are leaning) and not on a straight (because the bikes are standing straight up)?
Technically, contact occurs on the last straight into a corner (braking), or the first straight out of a corner (accelerating).