Background: My ex and I split up 3 years ago, well before I had DD, and we set up custody/parenting plan/etc a few months after she was born. I have sole custody and sole parenting time, although we've since added 5 hour visits every other week informally, without changing the formal custody papers.
Now: DD is almost 2.5, and I've been dating someone for a bit. It's not serious yet (he and I are both being cautious about jumping into commitment, which is nice), but the possibility is there, and we have brought up hypotheticals for the relationship. So my question is: at what point, if any, do I need to let my ex know? Maybe at the point of marriage (which is hypothetical at this point, of course)?
I would rather just not tell my ex at all, even after marriage. When I was pregnant, he got very upset and controlling/verbally abusive over the idea of me dating or having sex with anyone else. From the time of the breakup 3 years ago to now, my ex has been uncomfortably open with me about his relationship updates with dating, then engagement and marriage. And to a degree, a new partner now doesn't feel like it's his business, assuming that DD is safe. I'm also still a bit afraid that he will become upset and controlling again if he knows I'm involved with someone.
Other possibly useful information: because my new partner started out as a platonic friend, DD already knows him, and that hasn't changed since he and I started dating. She does interact with him and calls him a friend. He is safe, reliable, and DD likes him.