Hi Wonka,
In my state there is no such thing as separation, much less a separation agreement. You are either M or not. One of the things that my FIL told my W was as long as she didn't D me, she would still be libel for my debts, taxes on the house, etc. TX is a very odd state when it comes to D, I'm finding out. It's fairly easy to get a D and all it really takes is 60 day waiting period if the parties agree to everything. With kids involved it does take some extra paperwork but there are zero buffers or rules about cool down periods or counselling for kids, etc. Of course, since my W filed BEFORE she left, she had her lawyer LIE on her initial decree and say we had been separated for more than a month before she filed. When she actually didn't leave until 6 weeks AFTER she filed. It very rare for someone to file before they bother even leaving the family home.

So, basically, until the D is final, how we split custody is up to us. Since I am fighting to keep my home my lawyer has had to try and contact her lawyer to try and see if he is willing. So, until our M is officially over and done, there aren't any "enforceable" custody agreements.