If I were to tell her I support a separation, would it be better for me to leave( if she agreed to not hold abandonment against me in a divorce), or should I tell her I support a separation if she leaves, knowing she will take the kids). I believe that if she does leave, she will file for divorce at that time.
Don't tell her that you support S, just that you support HER. If she says she wants S, then tell her you understand and you support her decision. That's not the same as saying you want or support S. In Dobson's Love Must Be Tough he says it's like throwing the cage door open to the spouse that feels caged in. You're not kicking them out, just opening the cage door to show them you're not holding them against their will. But stepping out of the cage is a choice they must make on their own.
In general if the WAS wants S then it's best to tell them you're staying and that they need to leave because leaving creates hardships (getting a new place, moving stuff, getting bills set up, etc.) that the WAS should suffer through to help them understand that S is not all shiny rainbows, it can be a pain in the rear. Plus kids don't like being displaced, they want to stay at "home base". So this too puts the WAS at a disadvantage. But each sitch is different and sometimes there may be financial or other reasons that the LBS needs to move.
