New Jersey requires a written offer and acceptance for a valid real estate contract ("statute of frauds"). Furthermore, the contract is not valid for 3 business days to allow both parties and opportunity for attorney review. During that time, either side can cancel the contract without penalty with an attorney's letter. After that time, it becomes a binding contract subject to specific performance (you can force the seller to sell or the buyer to buy).
Most states, including MD, require a written contract for the sale of real estate for a valid sale to exist.
More than anything I would call what you had, or made, was a verbal offer. When the details were put in writing the two parties no longer agreed to the terms. And because in most states ALL real estate transactions must be in writing, it is just that more likely that you are not in a very strong legal position.
Please consult an attorney. I am not licensed to practice real estate or law in your area and my statement is nothing more than an opinion.