When dividing up assets the court considers four factors:
1. What each party had at the start of co-habitation - this dwindles over time and becomes part of the assets of the relationship to be divided up, so it is not necessarily true that a person will keep all of an asset, or its value, just because they had it when the parties got together (more to it but that is a simple summary). Length of relationship is relevant here.
2. Financial and non-financial contributions during the relationship - financial is obviously bringing in money, non financial is raising children, maintaining a home and helping to accumulate assets eg maybe doing the books for a family business. Generally these cancel each other out as they are seen as equally important.
3. Future needs of each party - most important factor usually. This takes into consideration each party's ability to earn an income and whether this is affected by things such as raising children, age, medical issues, disability, length of relationship and time out of work etc
4. If there is any need for an adjustment to make sure the division is reasonable - it is here that issues such as domestic violence, gambling money away, fraud come into it. The court has no interest in whether someone cheated or not, but it does make adjustments for dv etc.
You can agree to whatever you want but generally speaking where one party is the primary carer for children they will get higher than 50%. A common split, and remember this is a generalisation, is 60-40% in the caregivers favour.
If you reach an agreement about children and/or a property settlement make sure that you have it drawn up into Consent Orders and filed with the Family Court.
Get some legal advice from a private lawyer or a community legal centre.
Also start getting together all of the financial documentation of the relationship - stuff if your name, his name and joint names.