Hard to start when 30 degress or less out.

see if this forum helps you out.... https://www.google.co.uk/webhp?sourceid=chrome-instant&rlz=1C1CHBD_en-GBGB719GB719&ion=1&espv=2&ie=UTF-8#q=1993+Saab+900s+temp+gauge+just+completely+stopped

The fuel gage is most likely the fuel level sending unit inside the fuel tank, the temp could be wiring or the temp sending unit on the engine, try that first.

inside the fuel tank

Try to tightin up the light bulb. be aware the only way to do this is to remove the hole dash. if you do not know how to do this i would recamend you take it to a shop are ask me to go through step by step directions.

They are hard to release on all vehicles. You need to pull and release the tension with a wrench attached to the tensioner and slip the belt off the same time removing & installing it on

learn the hard way ,,, it will need the attention of a mechanic to change all the parts burnt when it backfired and caught alight ,or just write it off and call the scrapyard

Oil change interval has nothing to do with operating temperature. If your coolant is full, feel the upper radiator hose, when the vehicle is up to temp. if cool , thermostat is back from that hose,

Look for air bleeds, and read owners manual, some cars have coolant bleeds. Also, heater on high when filling coolant or risk bubbles...

My thought is that your fans may not be kicking in. They should cycle on and keep temp low enough. test them.

Since it does eventually start and run, hard starting is usually a fuel delivery problem (pressure regulator, fuel filter, fuel pump, kinked fuel line). First check the fuel pressure after turning the key on but not starting the car.

Have you tried replacing the coolant temp sensor?

If turbo in a temperate climate, use 0W40 or 5W40 synth for year round protection. If naturally aspirated, you can use the same or 5W30. If you live a particularly hot climate, 10W40 will work just fine too, and you might even be well off to go to 10W50, at least in the hottest months. Turbos generate a lot of extra heat which contributes to quick long chain molecule shear down in multi- viscosity oils. Accordingly, a 40 wt oil will quickly thin down to something more like a 30 weight oil. Oil pressure in these cars is marginal at idle, so keeping a close eye on good viscosity is pretty important, as that helps keep pressure up.