Personal Services Contract with Liquidated Damages

I have signed an employment contract that expires in June 2010. I signed it in March 2008. It says that if I want to terminate it I have to pay liquidated damages of $20,000, which is just under half my yearly salary. Since I signed it, they let someone leave without paying damages, they have laid off more than 10% the staff, my role has changed and they have forced me to add on extra duties and changed my schedule. Three weeks after my hiring they hired a new manager who is negative, and counterproductive. They are denying my vacation requests, which the contract states I am entitled to 3 weeks. In March 2009, I asked the General Manager to be laid off or let go by June 2009 as that's when my apartment lease is up and I want to move back home to Flint, MI. He said that won't be a problem. Now, they say they can't find anyone to replace me and I have to pay the damages of $20,000 if I want to leave. The contract is very one-sided and says they can change my position at any time, and terminate me with 30 days notice at any time. I just want a clean break, no severance, no unemployment. I found someone to replace me that they really liked, but something fell through and they won't hire him. How can I get out of this without paying to leave?