Hi E.,
The child who was born first has what is called "right of first family". That means out of his money the FIRST BORN child gets paid the full amount of court ordered child support BEFORE money is paid to any other children (including if you had other kids with the same dad that were born after other kids).
So, I'm not sure why you are being shorted..... sounds like his is paying you directly and voluntarily? That's why auto pay was invented. Haul him back to court and have him start to pay both amounts.
As far as what his financial situation is other than his obligation to pay what is awarded for your son, that's really not your biz.... so I wouldn't bring that up. is it fair? Hellz to the no. But life isn't fair. The judge won't look at that info, but he will look to make sure that your son is getting his full amount, as long as the dad makes enough money to cover his firstborn's award. Then he can pay whatever to any other kids, regardless of if he lives with them or not. You can have custody and child support decrees regardless if you live together or not - it's just a document stating financial arrangements. Sounds kinda smart to me. Looks like babymama #2 knows his deal. I certainly wouldn't stop support payments with someone who has a history of not paying what's ordered, even if I was trying to reconcile. Sounds like she just wants to protect her kid.
So, yes - take him back to court.
Good luck.