Hmmmmmmm...
"I made a sneak attack last Tuesday and I've been saving my Withdraw action. It's still technically after that sneak attack, isn't it? I want to withdraw now!".
Absurd, of course, and not what the OP is asking, but I think it's illustrative. Sure, the author should have been more clear about what he meant by "after" so each GM is going to have to define that his own way.
As for me, I'd define it in the same round. Withdraw is a full-round action. Normally there is NO way to attack (sneak attack or normal) AND withdraw in the same round. This Rogue Talent makes that possible. No more, no less. I think that's the RAI.
But if you WANT to sneak attack today and take your withdraw action next month, I suppose that's possible too, if the GM allows it. Probably not RAI.
Somewhere between my alleged RAI and my absurd scenarios is where the OP's questions lie. Not absurd (the OP's questions are fairly reasonable), but probably not RAI.
ex1: The hero did his Sleight of Hand out of combat. Then the guards start the combat. He wouldn't have a "saved" Withdrawal left over from his non-combat skill use. Probably.
ex2: Assuming you're already in combat (or else the 5'Step wasn't needed), our hero earns a withdrawal action but is unable to use it because of the 5'Step rule. Too bad. He cannot save it until next round. Probably.
Side note, I think "move equivalent" is not a Pathfinder term (I believe it went away when the previous edition became extinct). But no, I don't think taking a Move action would spoil the withdraw action of this talent, but you would have to do it all in one round: Do the Sneak Attack or Sleight of Hand, do whatever "move equivalent" action you're asking about, and Withdraw - that adds up to one Standard and TWO Move actions, a total of three actions in one round. Usually impossible, unless you have some other trick to gain one bonus action this round.