Re: Whats a contract?
A contract is an agreement between two or more parties, for the breach of which the law provides a remedy. That's the academic answer. In practice, a contract arises when two or more competent parties reach agreement on legal subject matter, and the agreement is supported by the exchange of consideration; there is an agreement when one party makes an offer and another accepts the offer.
However, your question goes well beyond whether you had a contract with your broker to correct his error. Contract or not, your broker has a duty to represent you competently and without negligence. You have an inherent right to damages for losses you incur as a result of your broker's negligence.
You don't say whether this broker was a loan broker only, or whether he/she represented you as the buyer's broker. I think the duties of a loan broker might invoke a different, possibly lesser, duty of competence toward you.
The broker may have defenses. These could include your inviting the error by (for example) making misleading statements about 3 points being OK even though your lender would have accepted 2, or reading and approving the erroneous document.
Unless deliberate fraud was involved, you won't be able to "take the firm to the cleaners." Instead, you should be able to recover your actual monetary losses, probably 1% of the loan amount, plus court costs. Whether you can also recover your attorney fees depends upon whether the contract contains a fee clause. You should also look to see whether the contract requires disputes to be arbitrated.