I think that Bud is wrong for making it seem like the OP holds all of the cards.
I think that you are equally wrong in saying that the developer has the position of strength.
Its easy to change a contract to correct errors BEFORE its signed. Its not so easy to prove that something is an error after all of the parties have signed it. Therefore I see this as more of a 50/50 situation than either of you are making it out to be.
The OP needs to give it a little more time for the developer to get back to him/her. Then, the OP may need a consult with a real estate attorney.