My husband doesn't want to buy house after I've put $20,000 deposit on it.?

My husband said to buy a new townhouse that I expressed interest in. He said it sounded great and that I should grab one before they sold out. So I put the $5000 deposit on it. About a week later he said he didn't want to go through with the purchase but then would change his mind again. I kept asking if he wanted me to back out, but he kept changing his mind or saying it was up to me. So the deposit became firm. Now, I've put a total of $20,000 down. That is all I'll have to give the builder until we move in. Still, my husband keeps changing his position whether he will sign the purchase agreement or not. If he doesn't, the deal won't go through and I'll probably lose my money. The other problem is, if I file for separation., I lose again. I am the sole breadwinner and a lawyer told me that my husband will get 1/2 of the equity of our current house and I would have to pay his at least $1100 in spousal support because of the inequity of our incomes. What should I do? Still file for separation or cancel the purchase and lose my dream house and $20,000? I'm really struggling with what to do. Any advice is appreciated.