"The Well" would be "Mark 2," yes.

That would overlook the fact that the Redbook songs were probably never written with a specific level in mind. Most likely, Parallax Software called up Mark Morgan (and the rest), asked if he could produce some songs for their game, and when he agreed, just stuffed it into the game's playlist and coded the game to play the songs per level in the order inputted--the fact the songs appear with those specific levels is more than likely a coincidence. None of the Redbook songs ever felt custom tailored for the levels they play in anyway, so I wouldn't really read that much into it.

As for the name "variants" syncing in with those levels, most likely that was done by fans attempting to give names to these songs before the formal names "Mark 1" and "Mark 2" were more widely known.

Personally, I would think the "Mark 1" and "Mark 2" song names would take precedent, regardless of what level they originally appeared on, since that's likely the names Mark Morgan himself likely assigned them. But that's my opinion on the matter.

As for Maximum's role in all of this, I think in the developers minds, Counterstrike and Vertigo both still take precedent over it, since Maximum is really only a PS version of Counterstrike pieced together after the fact to meet that port's needs and not much more. I would also imagine both Maximum and Vertigo were produced at roughly around the same time (especially seeing both borrow level design traits with each other) and likely overlapped enough that when they ultimately released to the public may not matter in this regard.

We also don't know when the music tracks themselves were originally produced. It's entirely possible both were produced with specifically Counterstrike in mind, but ultimately only one made it into the final game and instead whatever was leftover rolled over to Maximum and Vertigo instead.

It'd all be speculation on our part either way.

If you want a bit more fun with game11 take NIN's "Head Like a Hole" and play the bassline at just over double speed...

Weeeeeellll, that's explains why i couldn't find it.  Never mind, then.

The reason I ask though is that I figured since this would likely have text briefings if ever made, I thought I might try to make a new briefing track that hybrids elements from the D1 and D2 briefing music (in fact, I might do that regardless of whether or not the level set actually gets made), and I'd like to include that "whomp" sound for some percussion, but I'd like the original midi file for reference first if I can.

IIRC, that sound was an SFX file, not a MIDI. I remember seeing it in there with the rest of the game sound effects.