Jared, your question is not very clear at all. What is going up? The amount you have to bring to close? Keep in mind that if you're going FHA the minimum you have to bring to close is 3.5% of the purchase price, so on a $200,000 house that would be $7,000.00. There is no way around that (sort of). So if you were expecting less than that number, someone didn't explain the process to you. I would also note that in many transactions that's exactly what the buyer brings in to close.
Also, as to lack of clarity, you don't say what is being back dated.
As to your question about getting an attorney, I'm one of the first here to say people should get a lawyer, and this certainly sounds like such a situation. Keep in mind though that your remedy at this point might be to back out of the deal. So I doubt you're looking at a heck of a lot of attorney time.
One other option might be to find a new lender. It sounds like at the very least they are not very good at communicating. That would probably require the seller to consent to the change even if you could still close on the same time deadline. The need for seller consent would also be a question for a lawyer. Once when one of our buyer clients came to us with a lender in tow, and it became apparent that they totally sucked as a lender, we sent them to one of our preferred lenders even though it required a week or so delay in closing. Something like that might be an option for you.