Dear kangsy:

I would vote for leaving him as soon as possible, today. I would anticipate nasty things that he will post on social media. The way I would terminate the relationship: clear and Final. I don’t see a way to prevent his nasty responses. Maybe you can PLAN for it by posting your thoughts ahead of time, post what you intend to do and what you anticipate him doing (based on HIS past behavior). Post something like: I anticipate he will call me (this) and claim (that). Write the truth first, you introducing him to your family, being loyal and proud of him being in your life and him doing none of that, then what distortions of the truth he already came up with when you separated in the past and what distortions of the truth you anticipate him coming up with this time.

These are my quick thoughts, but maybe you can think about it more thoroughly and come up with a plan so to weaken what he can do next. I would definitely leave him for good.
anita