Your status says "MD/PhD Student," so is this the first year you are talking about? I think if you went through the match and then decline your spot then you cannot participate in future NRMP matches. So consider the prospect that you could no longer participate in the match if things fall through on this other place.
If it is for a PGY-2 or later year I would read the contract and see what it says. Signing a contract is likely legally binding, but the penalties probably vary from state to state and for different situations.