If you do "make it out alive" with your deposit funds you might consider reviewing the following document I wrote about buying from a Builder: http://docs.Steven-Anthony.com/BuilderRealtorAgent.pdf
Your situation, and others that have come up concerning builder purchases, is the reason I wrote the paper, which touches on a number of key issues you, and other potential buyers, may not have even considered:
Purchase Price vs. Market Value - Financing
The Phase-out of the “10 Year Builder Warranty”
Realtor®, Schmeal-tor. Who Needs’em?
Finding your Realtor®
(Be sure to review the section on Dual-Agency on page 4)
"Buyer hereby removes all contingencies. (once all contingencies are removed, whether or not buyer has satisfied himself regarding all contingencies or received any information relating to those contingencies, buyers deposit may not be returned if buyer does not close escrow. this could happen even if, for example, buyer does not approve of some aspect of the property or lender does not approve buyer's loan"
If you are already in escrow, I would not remove contingency until it was time to remove per your contract. Once you do, you will have little outs without the seller keeping your deposit. That is just my personal opinion.
I would highly suggest next time having a Realtor on your side of the transaction to help you out. Realtors can sell new homes and you always want someone representing your interest!!
So, without seeing the form, no one here will be able to tell you if you should sign it or not. You should have a Real Estate Attorney look at it at this point.
I have helped many of my buyers purchase New Homes and it I have run interference for them on many things, such as the interest rate that the "Builder's Lender", wants to charge, obtaining upgrades and more.
Hopefully, anyone reading this who is considering purchasing a new home will have a Real Estate Professional assist them from the very first time they go to the sales office to prevent the situation you are now in.
Good Luck to you and I really do hope it all works out.