How to get super-tight MIDI playback?

That’s not the same issue. That’s about how midi notes are recorded onto the piano roll, not timing instability.

I don’t think words can fully convey just how badly I do not want to use Ableton. It’s a culture I really truly do not want to be associated with. And I’m entirely too old for FL.

Just use the software that allows you to do what you want to do, what is this talk about culture and age?