I actually think that Gold just wants Emma to believe because then the curse would be at least partially broken and maybe then he could go look for Bae. And maybe that could give him his magic back. It doesn’t seem that he cares about Emma or Henry or even Regina except when he is using them for his own purposes which is to find Bae.
I don’t think it’s because he wants his powers back. We saw in “The Return” that he was willing to give up his powers. And besides, he created the curse so that he would be sent a land without magic. He new his powers would be taken away from him. So, he clearly doesn’t want his powers back. I think he wants the curse lifted so that he can leave Storybrooke and look for his son. The curse won’t allow him to leave Storybrooke.