Absolutely this.
He underestimated you.
This is who he really is.
You just didn't realise this because you do everything.
He slapped you and absolutely had no regrets afterwards or the following day.
Remember that.
His only regret is now your mother knows and he doesn't know who else.
He couldn't care less about you or your child.
He will promise the moon, cry for himself, and threaten to self harm.....anything to get you back.
He is a thug, no more, no less.
Both you and your child deserve so much better.
Report him to the police.
Thugs like him often threaten 50/50 childcare of children they have never done a thing for, just to regain control.
If you report him for DV to the police, I believe you can access Legal Aid, (i think this is true) which would be very helpful for supporting you.
Stay strong