What caused you to replace the thermostat in the first place? Like Steven said- check for water circulating once the engine is warm. If no water is circulating, it's possible that it's the water pump, which is a common fail on these cars, especially if it's the original one.
Additionally, DO NOT keep letting the needle get to the red- you're going to end up weakening/blowing the head gasket and/or warping the head. Once it starts getting close to 3/4, especially if the fan is running, something isn't right- shut it down, let it cool, and reassess the situation. On a properly operating cooling system, the needle should not move from the 12 o'clock position once it is warm.
The radiator fan not shutting off is concerning as well. Is the A/C switch on? Could possibly be a stuck fan switch.
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