Curious about coolant temperature sensor operation

Yesterday, while adjusting my throttle switch on my 91 hatchback, I had the opportunity to watch my radiator spew its guts out all over my driveway. Luckily, it did it at home as opposed to on the highway. Turns out, my battery moved up in the tray when I slammed on brakes the day before. The acid slid down the side of the cooling fan and ate a hole in the base of the radiator. Good job on my part for not going to the junkyard and getting the missing battery tie down. :banghead: Anyway, I jumped in the driver's seat and looked at the temperature guage. While not in the red zone yet, it was way higher than the normal engagement point for the cooling fan. Oddly enough, the fan never turned on, and my Check Engine light for high temperature never came on either. I changed the cluster in my car to the one with the tachometer in it, and its temp guage isn't near as sensitive as the one in the base cluster. This one likes to chill right in the middle except for the slight rise right before the fan kicks in. My old one would rise and fall as the temperature did. On cold nights, it would stay right near the bottom, and on hot days, it would be past the middle and be near the right when the fan would kick in, especially with the air conditioner on. My question is why did the fan never kick in when the radiator blew, and if my CTS never sent a fault signal to the ECM, should I consider changing it? I checked my old fan and it was in operable condition the day of the incident. I had to change it because it did not fit my new radiator bolt positions. And finally, I changed out the thermostat while the cooling system was drained out yesterday before I put on the new radiator. The auto parts store recommended a 192/200 degree thermostat. Other options were 160 and 180 degree. I assume these numbers refer to the temperature before the thermostat opens, but if someone could clarify this, and why I was recommended a higher temperature type, that'd be cool. Thanks.

I have no idea why they would recemmond a higher temp thermostat. I've always gone with 180 degree in all of my cars.

Any ideas as to the functionality of my CTS and fan... or lack thereof?