Talking to the Broker in Charge (of the office your agent works in) should go a long way toward solving your problems! I would do this today and see where you are after that.
If you feel this is getting into a legal issue, it would be worth a brief consultation with a local Real Estate Attorney to discuss your options. You have signed a contract, and there are remedies and penalties for breach of contract, just as you would have been bound by the terms of the contract. It's best to know your rights, so you know where you stand.
If this is "the home" for you and you have come so far, then you need to take a firm stance to make sure the other parties to the transaction understand your position. If your agent has not done so and you are nearing the end of the 60 day extension ask your agent to send the seller a "Notice to Seller to Perform". There is no real reason for a 60 day extension unless the seller is waiting for their new purchase to close and it is having problems.
Your agent should be doing much more for you than it sounds like he/she is. Go into the office of your agent and ask to speak with his/her broker.
C. Lee Miller - Broker Associate
CA BRE Lic# 01882648
Keller Williams LA Harbor
Why did you agree to a 60 day extension? It was your agent's responsibility to make sure you were making an informed decision. Maybe your agent and broker will have some suggestions on how to fix this situation and assist with some unplanned storage costs.