Can I pass the stress from the second half of PTL and still benefit from the second action?

What do you mean, like Fel uses PtL and Yorr gets the stress instead?

Yes. Although in that case Fel's ability does not trigger, but you get 2 actions.

Yes, you may. PTL says that you take the second action and then, after the action is already done, receive the stress token. It doesn't matter what happens to that stress token because the action is already over, you can't go back and undo it just because something happened later.

The reason cards like opportunist don't allow the stress to be passed is that they say "receive a stress token to do X", not "do X and then receive a stress token". In those cases getting the stress token is part of the price of using the ability, if you don't pay the price you don't get to use it.