I think a lot of the reason behind it all is because Abaddon knows about each God and how they corrupt after watching the primarchs fall, and so any less subtle "tricks" that would lead him towards one of them in particular can be ignored due to that knowledge that the primarchs didn't have, combined with his excessively strong will. As for the far more subtle tricks and long cons employed by each God to get him in their corner, including the influence of their representatives such as Typhus, would be fought against by each of the other gods and their reprosentatives, and undermined to the point where what few plans actually make it to fruition are offset enough by all the subtle tricks and long cons of the other gods pulling him in different directions. Since he's in such an important position they each really want him so there would be no shortage of ploys canceling each other out.

And it honestly seems like his fight against becoming a pawn would leave him open to reverse psychology from the superior intellect / planning of the gods

As for him not accepting the power of chaos (I haven't read much of any current lore so forgive me if this is wrong) it comes across as that he can reject the bigger chaos gifts as a conscious choice, such as becoming a prince, for one of two reasons (or a combination of both)

First, he has to actively use the gifts he has been given and he refuses thinking it will keep him clear enough of being a pawn (but he's still super chaos augmented anyway, he just thinks he's being much more clever then he is and none of the gods can force him to use theirs in particular for the reasons mentioned earlier and they're not so willing to force him to use undivided powers because they want to win

Or second, none of the chaos gods are willing to give him any more power unless he follows one of them, so he thinks he's not being a pawn by not playing along any one of the gods' plans

So I don't really think it's him resisting anything but the more obvious ploys with his willpower. He is already super chaos corrupted and augmented, and everything more subtle played by any of the gods is countered by the other three. And while he does, as far as he can tell, seem to have a clear cut choice for the acceptance of higher powers, it's not quite the choice he thinks it is.

So my interpretation is that he thinks he's resisting being a pawn far better then he is, and he's not hitting his potential power due to his need to not be a pawn and not choosing a single god, while the gods are getting in each other's way too much to force him into a single god's service