using the new rules, when you split you damage among multiple ranged targets, do you split ranged combat expert or enhancement??

RCExpert = No. It states (under the current rules) must be single target.

Enhancement deals one extra for each target.

So like say... oh... heck, Vt. Cyclops. He hits three people and has Psylocke by him. He can split his damage 1,1,0 and each of those damage will be increased by Psylocke (2,2,1)
He could also choose to go (2,0,0) leaving the enhanced damage (3,1,1)

If you want some fun pair a dual (or trishot) incap figure with enhancement. You'll not only give them a token (with possible push) but ping them for a point of damage. Even more fun if you crit hit and give them two damage a token with poss, push AND get to knock them back... and that's all to multiple figures.

another question, are you allowed to move diagonally??

yes