Follow-up on VC/VCG fix:
When they started pulling parts, shop found my small oil leak was from the Valvetronic motor gasket and not the VCG, also closer inspection showed no cracks visible on outside of VC and no leaks at VCG. At $56 instead of $940, I'm fine with that
On the minus side, it seems to have had minimal effect on my car's smell. It's more of a "deisel-y" kind of smell to me, not "musty" like I expect of mold/mildew, and definitely more sour than sweet, so I don't think it's coolant.
I'll try the ozone generator in the cabin anyway, just to be sure whatever's in there is dead - and will try running the car & AC while it's starting up - never though of that for my E30 but seem so obvious now that it's mentioned in this thread.
May also try that foaming stuff up the drain hose. And checking the drain hose to be sure it's connected... maybe do the check before I do the foam... first things first
Dackel thanks for the photos, definitely shows me what to look out for. Those cracks on the inside look like how I expect a "well-used" engine's VC to break down over time.