De-escalation is good. I'd suggest not putting yourself in a situation anymore where he can engage, such as thinking about changeover at another venue or supervised. Your call though, but I understand if you have your reasons for keeping it at your home.
Remember, you dodged a bullet with this guy - don't let the bullet shrapnel get you though.
The email to your L from XH is most likely an expression of impotent rage
I hope the new chapter in your and your son's book is full of wonder, excitement and anticipation, and has the happy ending both of you so richly deserve.
Cheers, DS
Me: early 40's XW: nearly 50 T: 15 M: 5 BD: Jan 19 S:10 SS: 22 SD: 24