My question involves divorce in the State of: CA

My divorce was final about a year ago. At the time of the initial filing my house equity was worth 210K, I had to revise the original split of assets about 6 months after initial filing and this is all during the decrease of home prices in CA. So the final number I put was only 180K of equity. From the time I last updated numbers and final judgment, the house had depreciated further. It's at 50K equity per Jan 1 county assessor- 4 mts after final judgement, so I can't take any more equity out to pay him his half (I already had a 2nd mort. LOC and it has been closed since the decrease in value).

I kept the house and had to pay half. My ex is saying I still owe him and is taking me back to court. How can I defend it? What are my options?