Load average of 400???
You could install systat (or similar) and use output from sar to watch for thresholds and reboot if exceeded.
The upside of doing this is you may also be able to narrow down what is going on, exactly, when this happens, since sar records stats for CPU, memory, disk etc. So you can go back after the fact and you might be able to see if it is just a CPU thing or more than that. (Unless the problem happens instantly rather than gradually increasing).
PS: rather than using cron, you could run a script as a daemon that runs sar at 1 sec intervals.
Another thought is some kind of external watchdog. Curl webpage on server, if delay too long power cycle with smart home outlet? Idk. Just throwing crazy ideas out there.
Totally agree. Have been there and done that quite a few times too.