Amazing project, great write-up. Would love to see a temperature graph as well! I'm wondering how good the PID controller here is working.

For future improvements, a cheap but effective win might be to put a temperature sensor on the oscillator (or two or three in various places). And use that to drive the PID loop.

Even if just experimental & not long term, it would be nice to have data on how strong the correlation is between the cpu & oscillator temperatures. To see their difference and how much that changes over time. Another graph! CPU vs txco (vs ambient?) temperatures over time.