Ha! I already found a work-around for #4. I wrote that bass part--I can write it again! So I'm currently writing a second version without the bridge and since I'm at it, without the second verse and with a lot of changes in the other verses. Going to import the MIDI, mute the first bass MIDI, and see if I like this one better. Got my fingers crossed it'll work okay with the RT bass on the choruses. Doesn't answer the question about changing a MIDI in the DAW but hey, it keeps me moving forward.
And yes, why yes, I **am** still working on this song at two in the morning... oops, lol...