I gotta say, this has been an uphill battle! I had the thing stable finally for a bit over 24 hours, trying different software to play back midis. Confident that the planets were finally aligned right, switched it to a different 486 with an old 3Com Etherlink III card instead of the Xirlink PE3. Put it in a permanent home in the basement.
It crashed doing network stuff a few hours ago in a way that even the TSR watchdog couldn't even reboot, nor a CTRL-ALT-DEL, squashing my earlier idea that maybe I could get the Raspberry Pi to emulate a PS2 keyboard and reboot the system when needed.
I think the next step is to get the raspberry pi to do waveform analysis on the output audio, and use a relay to pull the power if every other safeguard fails. 🤣
Edit: Or, maybe just heartbeating over the serial port.