<human>: Can you condense the text into a few key points?

I will try to keep this short, but it may not be after it's all said and done. My ex husband and I were careless with our taxes, he avoided paying a couple of penalties when he withdrew money from his 401k (about $8,000 worth or so) but now that we are divorced I am trying to make things right. I filed last year and come to find out we both owe the $8,000 to the IRS. I already filled everything out to get the weekly payments to the IRS started and I'm paying about $125 a week out of my checks. Now here is where I need advice, I have no idea if he is paying his portion or not and the IRS will not tell me if he is since we are divorced. I am fairly certain he isn't (won't go in to detail as to how I know) and I think I am left with paying the whole lump sum myself, and if I stop paying them they will just garnish my check anyway. Is there anything I can do to make sure he pays his part? I really don't want to get stuck paying the whole thing myself and he gets away scott free.
<bot>: Husband and I divorced but we owed the IRS, he's not paying his part and I am stuck paying the whole thing off.