Here's my notes on X59, mostly from the factory manual.
(1) Yes, starter.
Ignition to actuate the starter? I'd guess (2)
Pin (4) seems to be powered through the DME relay. Term 30 (hot 12v) is fed to the relay and (4) is connected to the +12v output [87] by way of weld (bundled red/blue) #26. I just checked on my '97 and it did stay powered after the car was shut off, long enough for me to walk to the trunk and check.
Note: I have not double checked or actually completed the swap, so use with caution...