1. Send all documents again since they asked several. If you don't do that, chance is your case will not be process further.
2. In the same envelop, attach a copy of your money order receipt, any evidence shows this money order has been cashed, and copy of the letter shows they have recived your payment.
3.Probably not necessary, it will take a while for Buffalo to receive your medical results. But anyway, to see what they response to your letter.