I don't understand...Why does vàng want the curse 'broken' when HE originally wanted it to find Bael??

...Because the curse trapped everyone in Storybrooke? They literally couldn't leave. Bae wasn't in Storybrooke, so vàng wanted it broken so he could leave and find Bae.

because magic is power qnd he wants power

I think it's because he can't leave town without losing his memories. (I haven't seen the một giây half of season two yet, so this may be inaccurate, but based off of what I've seen this seems like a plausible answer).