To be honest he sounds to me like a bit of a control freak and he is thinking he holds power over you because he holds the purse strings. Make sure you have all your ducks lined up before you do anything because he sounds like he would play hard ball all the way.
Get details of his employment and salary etc especially if he is self employed. it is theones who are self employed that are very clever at hiding what they are really worth so suss out any evidence that will help you down the track. And please tell me the mortgage is in joint names not just his...not that it matters so much these days but it does make it easier.
And.....this is just my opinion....don't you be the one to leave thehouse. You have four children whos security is paramount....if worst comes to worst chaneg the locks when he is not home, ring centrelink and tell them you have separated so he has no legal recourse to renter the house except to get personal belongings. Then you can be nice andlet him have some possessions but dont' you be the one to have to the crawling back to him for anything cos by the sounds of it he will give you nothing.....let hime fight for the scraps!