I don't think the DSMB can go direct to the FDA. They are independent for a reason but they are also only looking at very specific details of a trial, i.e. safety. They don't seem to have any reason to look at anything else but in this situation, when the primary outcome is life or death, safety IS the measure of whether the drug is working or not.
Others might have better understanding, but it looks that the DSMB is asked for and paid by the sponsor. There conclusions are then given to the sponsor and the sponsor would then use it as they see fit. Unless there is harm, it seems they can halt a trial if that is the case. However, it seems also that the data the DSMB is looking at is also being looked at by the FDA. Really difficult who talks to who.