Want to seperate but my husband won't leave; can I take the children?

If there are no court orders in place, yes, you can take the children and leave.  You don't have to file for divorce or custody first;  it would be a good idea to arrange ahead of time, to file for divorce, or for custody and child support if you don't file for divorce (and you can ask for these immediately, in a motion in the divorce case once it's filed), as soon as you do move out.  Being the one who files first sometimes seems to make more of a difference than perhaps it should.

Technically, by moving out, your husband could use abandonment as grounds for divorce, but I doubt that this would make much difference, if any, in the outcome.  And custody will be decided based on what's best for the children, where his emotional abuse will count for at least as much as you moving out.