Diane: You need an attorney on this deal. The Bank has one and unless you're very clever, that makes the opposition more talent heavy than your team. (Sort of like not having any line backer in your football defense line-up.)
Now, I'm not an attorney so I can't tell you what you've got there but it seems confusing to me. If the sales contract is signed by both sides, that means, subject to any contingencies, it's a deal. If the bank has already signed the contract, it has approved of it, I GUESS. In NJ and only NJ as far as I know, there is a three day attorney review period, during which your attorney can void the deal and, if there is interest on your part, suggest provisions that make the deal acceptable. The other side can accept or continue to negotiate back and forth. YOU CANNOT VOID THE DEAL YOURSELF AFTER YOU SIGN IT. (Except, if the bank has not signed it, you can withdraw the offer. That's not voiding a contract, that's rescinding an offer.)
As far as deposits go, they should be spelled out in the contract, both as to amount and as to when due. If you fail to make them on time the contract becomes "voidable." Some deals are negligently managed and the provisions are not always done. There still can be a closing and you can take title but if they are not done, it opens a big escape door for whomever wishes to use it.
Since you have these questions and, for whatever reason(s,) have not asked your realtor them, I'd say, yet again, get an attorney. You are playing with major investments and costs. Don't get stuck behind the eight ball.
Enough sports references. Best of Luck