Fast idle, low idle, (stalling) temp gauge all over the place.

I was preping / preparing to do the mohave trail Saturday morning and I had to run to the store about a 1/4 mile away. When i got back I took off the radiator cap it spewed out some coolant. I didn't have time to let it cool to top it off again thinking I didn't loose much and it's plenty full ! Big mistake ! About 80 miles into the trail my VX started idling fast, 1500, then it was like 2500, water temp was normal all the way. I would stop and leave it in gear for about a minute and it would go back to 750-800 then I would continue for a hour or so. This lasted all afternoon and into the night. When I got to Laughlin Nevada 134 ++ miles of dirt road and sand washes. I let it sit over night, checked the oil and gave it a long look but my dumb brain forgot to top off the radiator. We were out in the boonies and when I stomped my brakes for a rut or rock I noticed it idling fast again. Then soon after the engine light came on, then the temp gauge started moving to 3/4 when I hit the brakes hard to avoid things, then my idle was so low it would die, I headed for Baker calif to refuel and check things out, I know better than to try and top off the radiator when it's at running temperature ( it just spits it out) so I just freewayed it 70 miles home watching the temp gauge. Made it home.

This morning I filled the radiator with about 3/4 of a gallon. Started it up and it died, restarted it and held the idle up and drove it around, about 5 minutes later it would idle, then soon after it started idling fast again, I drove about few minutes and it went down to normal.. drove it more and about 10 miles later and the engine light went out. I parked it for a hour and I drove it to work and put 50 mountain / freeway miles on it and all is back to normal !
Hummmmm.