Just read through your thread... I'm kind of a GM guy and some things stuck out at me.
First, the 2200 in your Sunbird is a pushrod OHV engine, the DOHC Ecotec replaced it in the J-body in MY2002+.
Second, you're not going to be able to do what you want with the TCC and a simple external switch. The 4T40e is entirely electronically controlled and the TCC is modulated with PWM, if you some how modify it to run with on/off states, you will burn up the clutch and have no TCC. It's not a particularly strong transmission so it is good that it's in the hands of an ecomoddder...
Third, almost ALL GM cars are bottom breathers... the holes in the front fascia are there for design only, not function. The air dam blocks the air moving under the car and forces it to travel through the radiator and back under the car. A lot of GM cars that run hot on the freeway are missing that air dam, and most of them live in snowy states.
The car most likely has a standard GM thermostat value of 195F, running up to 210F in traffic is nowhere near overheating. If you think there is a problem though, I would definitely check/replace the thermostat as a first try item as they have been known to get stuck or not fully open.
Last, the e-brakes in damn near every GM car up through the mid-2000s are pure crap.