I think Rumpel is neither good nor bad. All of his deals are for something that is a gain to him. He doesn’t care about other people (except for Belle and his son, so far) and so if bad things happen to them because of his deals it’s not because he specifically meant to be cruel but because he simply doesn’t care, to him it’s their problem and not his. So long as he’s gaining something that’s all that matters. So even if his end goal is to break the curse that still wouldn’t make him a good guy because he wouldn’t be doing it for the others, he’d be doing it for himself. Probably because even if he has some power in SB he doesn’t seem to have as much of it as he did in FTL.
As to why he didn’t accept Belle’s kiss, I think he did know it was true love but just because he’s got all this power now doesn’t mean he’s not the same coward he was before. He hates what he’s become I think and not so much doesn’t believe she doesn’t love him but rather is too scared of the idea to allow himself to believe it. He’s scared of the possibility of her love not being real, in which case he’d end up hurt and alone without his powers, but he’s also scared of it being real and then somehow losing her or things going badly. He did lose his previous wife after all. I think the very idea of loving someone or someone loving him scares him to death so he chooses to ignore it and tries to convince himself it isn’t real.
Rumpel is really complex and is actually my favorite character, I really look forwards to getting to know more about him and seeing both his past and the way he’ll develop in the future ^^