OK Judd, I feel you pain, but look at it this way; you've done great preventative maintenance where it should be done. Because it seems to be related to temperature I have a suggestion that could be a very inexpensive part(especially compared to what you have spent thus far). It may not be engine temperature, but rather the temperature of the main fuse under the hood.

On the drive's fender wall (up toward the firewall) is a main fuse in a plastic holder. The fuse connection tabs and particularly the fuse holder connections can get corroded (even thought they may not look like normal corrosion; maybe just discolored or glazed from the heat), causing high resistance, which causes high current and overheating the connections the longer the car runs. Eventually, it will starving the computer signals for power. This in turn causes the computer to get wacked out with weak signals (could explain various sensor failure codes that computer is seeing) and eventually stopping the engine.

If want to try and clean it you can, just to see if any improvement, but I would suggest you get a new fuse and good weather-roof holder. It's cheap. You might find something to do the trick at a place like Radio Shack until you good replacement. My son has a marine grade holder in his 89 240.

Hope this is the problem. Symtoms sound like it.

Gary