if my herald has say pulse wave and i give him a free action via galactus' revenge tokens to use it. afterwards i know i cant give him a free action to do it again, but can I give him a ranged combat action to use it, or is it once only no matter how i activate it?

From what I understand, if the herald uses PW on his own, you could activate it again as a free action via the revenge tokens. You wouldn't be able to use it a 3rd time though as you already used it as a free action once, but you'd be free to use RCE or whatever power hasn't been activated via the free action granted from the Revenge Token.

Yes, the restriction on using free actions to do the same thing multiple times is just that, a restriction on how you use free actions. Non-free actions are irrelevant to it. Feel free to do Pulse Wave twice under these circumstances. Be sure to grin like a silent film villain while you do it.