Ok, your emotions are going to be all over the place. That's normal.
The money side of things though, you will have to think very carefully about and consider the type of person your OH is. Will he be amicable or fight for every penny?
You are not married. So whats yours is yours, what's his is his. The house is in joint names, thats a good start. Means he can't just sell it without your permission.
However, the other house, if thats not in joint names then technically its just his. Unless you can prove you paid towards this house (either capital or towards mortgage) then courts will consider it to be his property. Not yours.
The washing machine, TV, bed etc. If he paid for it, its his. You paid, its yours. Best thing to do if you were SAHM is to agree quickly how things will be split.
Financially he only is liable to pay maintenance for whatever the prevailing CSA rate is. That's usually 15% for 1 child, 20% for 2 and 25% for 3+. Check out the CSA website for a calculator.
Until you sell the house or transfer the name to single owner, both of you are liable for the mortgage. In practice the bank won't care who pays, so long as one of you does.
What you need to start thinking about is if you can afford to stay in the current house. You may understandly want to to minimise disruption for the kids but practically it may be impossible. It may be better to cut your losses now, downsize and be happy rather than struggle on in debt and begging ex to help pay mortgage.
Lastly, pop over to entitledto.com and see what benefits you are erm...entitled to!