I really think you need to set some hard boundaries regarding the exchange of your son. For a VERY long time your son or H has you driving all over and often times changes the time/location once you are en route.
You will be much better off when you have something in writing (legally I mean) about the exchange of your son including the exact times, locations and days. Your H is walking all over you when it comes to exchanging your son. There is to be no chit chat at all. Get your son and his things, get him in the car and go. A solid parenting plan, not your son or H, will call the shots when it comes to time to exchange. This has gone on way too long and it only hurts you more. And it gives your H more power to abuse and use you. Your H knows you will do anything for him no matter how poorly he treats you so he takes advantage of you at every turn. Only you can stop that.
It is your H's problem if his new baby is born when he has your son. It is up to him to make appropriate arrangements for his son if this happens on his watch. Do not assist your H. Do not talk to your H ANYMORE about anything unless it concerns your son in the here and now. It is outlandish that your H expects you to assist him with childcare when his new baby arrives with his mistress that he left you for begins labor. And you have to let your H know that. When your son brings up anything about your H or the new baby redirect the conversation to something else until you have a better handle on things.
The reason your H is so abusive to you is because he *is* guilty. It is psych 101. The more he can tell himself that you are a pain in the ass, you are standing in his way to happiness, you are holding up the divorce and this mess is ALL your fault the less he will be required to examine himself. And let's face it - with a new baby on the way he won't be directing any energy to self improvement.
Stop giving your H so much ammo - the crying in front of your H must stop. Having your little son protect you in front of your H must stop. If this is something you are unable to manage at this time then find a third party to handle the exchanges even if it means you have to pay them a weekly fee to do so. Or, see if there is a "child drop off center" close by. The family court should be able to help you find one if one exists in your area.
Honestly, if your H found out about the treatment program it will probably just fuel more disdain. He wants out and anything that happens that will prolong you wrapping up this divorce will annoy him and in turn he will treat you worse. As time passes he will see a whole new you (much stronger, able to establish and enforce boundaries) and then he can wonder what he is up against.
You want something different but you keep doing more of the same. You have to try.
