setting boundaries with DCs after split

[alonely]

Hi,
have been in very messy relationship with father of DS. We haven't lived together, lots of emotional abuse, EA that turned into real one etc. I do want him back (no comments on rights or wrongs of that one pls). But need to rely on him for childcare and tbh think I want to see him or to test that he is still committed to DS. My MIL is helpful sometimes as intermediary.
Anyway last weekend, I saw him while he was looking after DS, stayed the night and was told the OW was coming round in the morning. Set condition that she didn't see DS but relented when told he would be at mine that night. All ok, but then DS (he's 3) let on he and ex had spent the day with OW and been to her house. All went up in flames. He has not told her truth about us either. So pretty messy.
No idea where me and ex are but wondering is my demand that DS doesn't spend time with OW reasonable? MiL seems to think that's ok. But his standoff is not to see DS. We go round in circles. Boundaries need to be set re DS and OW etc but what should they be?
Open to suggestions. Anyone been in such a mess as this before?

[knockedupagain]

I personally don't think you should stop DS from seeing his dad, and I think that means you have to accept that if he has someone new in his life, then that means DS spending time with her too. As you've discovered, you're powerless to police any rules you set over this anyway. It would be very easy for DS to get caught up in the middle of this, and feel he is betraying one or other of you no matter what he does. If DS has no issue with spending time with your ex's new partner then whatever you may feel (and I can well understand your hurt) I think it would be best if you try to deal with it without trying to stop it. It is all too easy for non-residential parents to gradually see less and less of their kids, and putting barriers in the way of them spending time together heightens that possibility. Put DS first on this one.