Right, it's generally something "simple", that is, in hindsight which takes time to acquire
All this detailed tech stuff will definitely give you the gift of humility at some point.
Believe me, even after you get "good at it" -- you'll still pull some mistakes that seem extremely dumb after the fact, rarely do you make a "complex" mistake.
Yeah, you're going to need to have some vacuum to spin one of these guys up much. They tend to be pretty good turbines, and so do a lot of work if there's air there, and that driver won't provide much energy to do work with. You should be able to adjust to target RPM with a decent vacuum and a scope on one of the drives or the hall to measure the frequency. The pumping speed is a real big function of this, so you want fast, but not so fast it flies apart of course. IIRC the pump speed is at least a function of RPM^2 if not a larger exponent. I take advantage of that here in my fusor run modes, where at full speed it would be drawing too much power at the gas pressure; I run at about 1/4 full speed for that.
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.