Found something that would read any .dmp files for me, and got HWMonitor, and now I can't reproduce the crash.
By which I mean I just played for about 15 minutes in fullscreen including running through the same two areas of heavy activity and getting caught up in a battle with numerous enemies who killed me dead, and everything was fine.
I checked HWMonitor a couple times during that and the GPU temp never got above 62 degrees Celsius... and I believe that's well within the safe parameters for the card.
So now I don't know what is or was going on. Granted, that was a small playing session, but for the past week I couldn't go 50 yards without the game crashing.
I'm wondering if it did have something to do with Steam crapping out somehow, that issues seems to have been resolved this evening - either on my end or theirs or both - and since I stopped having problems with that, no game crashes either.
Now I think I'll put back the newer mods I removed and see what happens.