Sorry girl, only just found your new thread!...my bad.
I have been reading your troubles and they don't seem to be changing much. I think the answer lies more in you than anyone else Exh included. You know he isn't going to change in the near future if at all. So, who CAN change?...you can. There is only one person that is getting all stressed by his behaviour, that's you.
You DO know that you and only you are responsible for your own feelings don't you?. It's totally up to you how you react to things and how you let them affect you. Maybe it's time for a more introspective look at YOU.
I am not trying to blame you, I trust you know that, but I was holding a lot of bitterness towards my W and one day realised that the only person that was hurting about that, was me. The more I let the feelings affect me, the worse they got. It's not easy AT ALL to let them go and I still struggle myself from time to time, but it's a revelation to know that you CAN change.
Regarding the CS....I call total BS on his hardship. Demand what is your by right and create a stink if you don't get it. Maybe threaten to tell his family that he isn't paying for his baby. That will make him think a little if he is trying to be the 'good dad' in their eyes. I remember my W having arguments with me about 'her' money and how she couldn't afford to help pay the monthly bills whilst we were still together. Since she left, she's managed to pay rent, gas, electric, rates, loans, car, fuel and STILL buy new clothes and go out....Suddenly she CAN afford bills...figure THAT one out?...BS again.
Anyways...hope you can take a little time to think about how you REact (capitals on purpose).