If your ex is acting like a pig's backside instead of an adult, you may need legal protection to control him. He has no right to barge into your home and terrify you or your guests. So first off, I'd be mentally prepared to report him for domestic violence and in the meantime inform him calmly that this will be the consequence if he ever behaves badly again.
It is very important for your son's wellbeing to see adults behaving as adults. He may years in the future feel he is to blame somehow for what went on. The only way to alleviate this is for everyone to agree to ground rules, including politeness and especially not using son to carry messages about what mummy / daddy said about XYZ.
This is a counsel of perfection, and if your husband won't abide by it it is his child who will be the loser. Sad he couldn't have kept his trousers shut and stayed home with the both of you, but that was his choice.