In Sept of 2015 my partner and I bought a house together…

In Sept of 2015 my partner and I bought a house together after both selling our individual homes to purchase it. We each have 2 teenagers - 4 kids altogether. At the time I was earning 100K as a teacher and he 350K as a financial advisor, however we both contributed about 250k each from our homes at that point. We went in to the marriage with no pre-nup and were happy with the arrangement.
The following July (last year) he lost his license and had his business bought off him in a compulsory purchase. The price was approx. 1mill. We got married 3 months later.
The purchase of his business was made in an agreement last Oct, of 3 payments: 600k last Oct, approx. 200k this month and 200K in 6 months time - with tax needing to be paid from it.
Our home we purchased had to be sold as we could no longer afford it with just me working, and lost $300k in the sale.
My husband announced last week he wanted to leave me - ironically just before the 2nd business payment is due to come in.The home is due to settle next month however Todd is refusing to sign the settlement papers unless I agree to make no further claim on our property via the family court.
There should be about 500K coming from the settlement and he is agreeing to give me 250k from this ONLY if I make no claim on the business he lost during our marriage - probably another $300k in 2 further payments.
Since July of last year I have been the sole earner in the family, supporting our family of 6. I have made him an offer of a 40/60 split, myself getting about 320k, him 480k, but he has refused. I think this is very fair, considering. What is the legal standing with no pre-nup and the intention of going in to a marriage 50/50 - then me being the sole earner? Thanks - Sonya