Shannon...looks like long time no hear.
You have a 94 SSEi I assume from the coupler and dash issues. The crazy gauge issue is one that we have a couple fixes for...option A replace entire cluster, option B replace a small circuit board behind those three gauges. When i had a 95 I found replacing the small board to be quick, easy and no worries about the mileage etc.
The coupler will only correct the rattle like noise from the supercharger. Running at 200-220 in traffic or sitting still is normal. The fans come on at 215 and 225ish.
The Bzzzzzz you hear when you turn on the key before starting is the fuel pump running to pressurize the system, also normal. (And a good sign)
The missing once warm.. You mention new plugs/wires. What brands did you install? I would try removing the coils/ICM and cleaning the plate the ICM mounts to and the bottom of the ICM to ensure a good ground connection. Look over the ICM for any cracks etc, check connectors and wiring for any loose or bad areas.
00 Regal GS: All kinds of cool stuff.