It's none of your ex's damn business, & he didn't extend the same courtesy to you - so why would you bother?
even after 10 years apart he still tries to control /abuse me when he gets the chance.
Aha. And yet you feel it "wouldn't be right" not to tell him - what do you think lies at the root of that?
Are you still subconsciously in thrall to him? Seeking permission?
We only speak when we have to and its only ever about DD.
Please, Fairycake - KEEP IT THAT WAY.
If you tell him about your b/f, he will use it against you in some way. He will feel he is "owed" information about you, & be delighted that his control over you still compels you to tell him things that are none of his business. DO NOT MAKE IT HIS BUSINESS.
If your relationship goes the distance, your ex will hear about it organically at some point. That will STILL not make it any of his business.
I'm a bit concerned about the fact that you are wrestling with this non-issue as if it's a moral dilemma. Did you have counselling after escaping your ex's abuse? Do The Freedom Programme?
If you are feeling stressed about a need to 'report' to your abusive ex, he is having too much effect on you & taking up too much of your headspace. It's never too late of too early to reinforce your sense of self & boundaries by engaging with - www.freedomprogramme.co.uk/online.php
Say nothing to him.
As & when he finds out you have a b/f - you STILL say nothing to him.
It's quite likely he will look to use it as a stick to beat you with, or a topic he can use to re-establish engagement with you.
The fact that you feel the need to tell him ANYTHING unrelated to your DD's needs means you are not quite over the control he exerted over you.
You are looking in some way to 'behave honourably', as if we can make other people behave well by demonstrating that behaviour ourselves. With abusers, that always backfires. They take your honourable gesture, twist it to their own purposes, & never reciprocate.
Resist the urge to tell him anything, it will pass ...