Say I have 30' movement. Can I run up to a creature 15' away, swing at it, and run back 15' without spring attack? I know I would normally suffer an AoO but not sure if you can take part of a move, take an attack, and finish your move.
If you can, what page?
No you can't. That's exactly what spring attack does.
No, you get a move, then a standard, or a standard, then a move. You can't "split" your move without Spring Attack.
EDIT: Look at the Normal explanation below Spring Attack that tells you the difference between having the feat and not having it:
Normal: You cannot move before and after an attack.