Wow. That guy is batsh*t crazy. For some reason, reading about him makes me swear alot.
This is another intimidation ploy. Don't fall for it, stay strong. Remember just a few weeks ago you were too scared to do anything and you have been AMAZING in sticking to your boundaries and protecting yourself and kids.
Do not fall victim to fear. You are the sane one and you will come out on top eventually. But absolutely, you NEED to document every single thing from this point on and everything you can remember. He is playing dirty, you need to not worry about bringing up his drug use or trying to mandate treatment for him etc. Bring out your guns, you have them where he does not. You don't need to fight dirty, just telloing the truth should be enough.
Document document document every single email, message, call, anything you hear thru his or your families, anything that happens with your kids, keep your house clean in case CPS drops by, and most of all be gentle with yourself and KNOW that you are doing the right things.