OK - I just can't leave well enough alone...
This is your child. Do you have a suspicion that something is going on? you need to act on that suspicion thru whatever means are available to you.
You seem to have a lot of reasons why you cant do something.
this would be a good challenge for your self esteem -and it should make it easier because you aren't doing it for yourself you are doing it for your child and trying to protect your child. Come up with a game plan as to what you can do to help your child.
Check your divorce and child custody agreements and see what he is and isn't allowed to do and find out how to make him live up to it.
You are tied to this man til the child is 18 -- you both need to figure out how to work together..
I'm super curious - in this thread
http://www.tfproject.org/tfp/showthread.php?t=104809 - you said your ex got unemployment in the summer - what kind of law does he practice that he's got that arrangement?
From the threads you've posted there are issues with your son's behavior, there are issues with your ex paying support, there are issues with your relationship with your ex. You've got to start somewhere... Do you really want to spend the next 15.5 years like this?
Most lawyers will give a free consultation. I'd also google some resources that might be offered for free to you in whatever town you happen to be living in... (terms to google under, WOmen/child support/divorce/custody/etc...)
Start your list of all the issues that need addressing then prioritize it...