Thanks for the feedback. Regarding the volume of the bass part - it completely depends on needs of the composition. In my view, the bass is not too quiet in this song relative to the information it conveys. If the bass carried the song in any meaningful way, it would be louder. I think people should divorce themselves from notions of how a rock song (etc.) should sound when they listen, and ask if there are any particular music ideas that are being obscured in a poor mix. That might be the case, as you suggest during the E-C-E-C part, but the goal at that moment is to actually slow the listener's pulse, so the speak... so it makes sense to begin emphasizing every other measure with the bass, instead of every single measure. I believe I manually faded down the C notes to make them softer.
The middle section does modulate - to B minor. I just don't hear it modulating to G minor. I don't know why that particular choice would sound better. Just me. There isn't supposed to be a particular moment when the main key obviously comes back. My challenge was to slowly blend the middle section back into the main theme. Maybe I didn't succeed there, but that was the aim.
Sometimes, I feel that people simply point out things that were done intentionally as if they were errors... i.e. I know that the main theme come back slower at the end... It's not really supposed to have more raw energy than the first statement of the theme, for reasons that have to do with the implicit narrative of the song (Google "Three percent"). Perhaps I could record another version of the droning E static guitar, to flesh it out when it returns. That would aid the narrative of the song.
I'm definitely not happy with the current vocals. The main thing I want to change is to recruit other people to sing, so that it sounds like a true group singing, not like overdubs. The "ohh"'s in the quiet middle section will be handled by a female vocalist. Anyways, thanks again. I play with a jazz bass... I'll consider getting more flexible pickups installed.