Helena, I think your plan of action should depend a lot on the level of abuse you endure with your husband and whether he abuses the kids. If the house is generally peaceful (like no shouting, verbal insults, physical violence, etc..) and the kids are happy and thriving with both parents then you may be better off waiting indefinitely to separate. If your husband is bullying everyone in the house though, including yourself, and the overall dynamic is negative and everyone feels afraid, then you and the kids might both be better off leaving.
Another consideration is how separating or divorcing will affect you and your kids financially and logistically. Is it a practical option? Will you be able to maintain your kids standard of living when they're with you?
Finally there's the question of whether you plan to start dating right away and seek to re-marry. If so then you may wish to think how that will affect your kids and also consider the risks of starting over with someone new who will have their own baggage and flaws. If you don't plan to date or re-marry then there's no pressure for you to divorce quickly for that reason.
Some of your misery might be reduced as you further build your own new life right within your current home. You can probably do a lot of things like the sorority alumni group to stay busy and active so maybe that'll help, but the key factor seems to be whether your husband is an abuser and if you need to separate for the welfare of yourself and the kids.
