It's also not uncommon for people in domestic abuse to stay longer than they should.

Yeah, when they have genuine fear from their partner. Nothing you said here shows any sign of being feared of him.

I did actually leave briefly but took him back after a few months as I still felt we might have a chance.

You didn't explain anything. You left him. You took him back, and he did not show the signs of his previous abusive behavior. So why did you took him back, in the first place? It's clear the abuse wasn't your only problem because you still want to leave him after the abusement long stopped.

also I keep wanting to find the right words and time

There are no right words, nor right time. You want to get separated. There are no words that would make it easier for either of you, also there is no good time for bringing this up.

he just springs the questions about whether I love him or not.

As you are about to leave him, it is a perfectly understandable question from him.