you are in trouble. ask for extension of closing date ASAP if you still want the house or talk to the seller trying to get some of your EM back. unless you can get a letter from the lender saying that your application has been rejected, you are most like will lost your EM.
commitment letter doesn't worth the toilet paper you use to wipe your ass. Locking rate is the real deal. Agents spend money to lock rates. They can lock 30 days or 60 days but the longer the lock the more expensive it gets. So lock rate if you feel it is the right rate and make sure closing happens before the lock expires.