It’s really important that you DON’T SIGN ANYTHING, especially a document prepared by your husband or your husband’s lawyer.
You’ve asked a lot of questions about separation versus divorce. I’ve got some answers here:
http://www.ottawadivorce.com/divorceprocedure.htm
But I think that instead of worrying about all the legalities of separation and divorce, you’ve got to focus on the children and the financial issues.
If you’re husband’s abroad and you’re at home with the children, you’ve most likely got a right to child support. You may well have a right to spousal support and as logicalvelocity says, possibly the right to stay in the matrimonial home.
You should consult with a lawyer at least at first to fully understand your legal situation. Most places have a legal aid or similar program to help people in your situation obtain legal help. As well, a lot of lawyers offer free initial consultations