separate property and the Marsden calculation

I have been married for 2 yrs, 10 months. My house was my separate property for 10 years prior to the marriage. He has been on title for 2 yrs, 10 days.

So he wants his cut of the house. The value on the house at the time he went on the deed was 685k. We took out a HELOC and built on to the house, however, the contractor abandon the project and there is over 100k worth of damage to the house.

I had the house re-appraised in June 08 and it appraised for 635K.

Also, I have been making payments on the house with separate property funds (Disability) since may 06.

I am re-financing to assume all financial liability for the house and combine all community debt. I can not afford an attorney, so I am doing this on my own. Can someone please help me to calculate what his interest in my house would be?

Total marriage time: 2 yrs, 10 mo
Total time on title: 2 yrs, 10 days
Value in 12/05 685k
Value 6/08 635k

Thanks for your help