Separate them NOW before someone is hurt or killed. Nippy tetras and Angels don't make good tank mates for Bettas.
Bettas do best on their own.
Here's our Betta Care Guide
Is this the same betta that was recently forced to fight?
The 55g isn't an option. There are Tiger barbs, guppies a an RTS in there?
Unfortunatly, he's not going to be any safer in that tank. Seriously, he needs to be in a 5 or 10g tank by himself.
I don't mean to be harsh, but you're risking his life.
Oh whew, ok, I thought you meant the Betta.
However, you'll want to keep a close eye on the Angels and Betta, they're really not compatable. Read the Betta care guide I linked to.