Honestly the temp gauge sounds correct. The gauge on my 99 starts at 160, norml runing temp is 180-190. The neddle really does not move, but the gauge goes a lot higher. I replaced my coolant temp sensor thinking there was an issue. It was normal and I read the temps with my scan tool to verify, the gauge was correct.
For the power sunroof issue. Mine also needed help to close, not all the time but it did open and close slowly. Sometimes it would stick..
I did this mod here...
ZZ Performance
And it fixed it! It opens perfectly every time now. It is amazing what grounds can and do, do! Check it out it is free and cannot hurt.
The water on the floor could be clogged or disconnected sunroof drain hoses. The run from the roof, down the A pillars. The water on the pass floor could also be from water entering through the blower fan. Search the site here, there are threads on the issue and how to fix.
My washer pump was bad too and leaked. Get a new pump, usually $10 and also the rubber fitting. If you cannot find the fitting, just use a scrap piece of rubber hose. The rubber cracks as it ages. I repalced my pump and still had a small drip, then I replaced the rubber fitting. No drips now!
Go to a Pontiac dealer with the cars VIN and ask them if the oil issue recall has even been done. They will be able to tell you.
Poor fuel milage could be a very diry air filter, or failing oxygen sensor(s). Replace the filter and monitor. If still bad, go to rockauto.com and get both O2 sensors, they have the best prices. It probably would not be bad to replace them, due to mileage.
