Temperature gauge sits on cold?

Yep, I agree the thermoset is to blame or you are low on coolant. Here is a video to show you how to check the coolant.

https://youtu.be/GSE9skKnOgY?si=pXrwEjZjvSaqRsEZ

Here is a generic guide to help you step by step with instructions in the diagrams below to show you how on your car.

REMOVAL
1. Ensure engine is cool, then remove radiator cap and open draincock. Allow coolant to drain below level of thermostat housing.
2. Remove air intake tube and disconnect water thermo switch connector.
3. Disconnect engine wiring harness ground strap from connector above housing.
4. Disconnect exhaust gas oxygen sensor electrical connector, then remove upper radiator hose from housing.
5. Remove thermostat housing retaining bolt and nut, then the thermostat and gasket.

INSTALLATION
1. Clean mating surfaces of housing and cylinder head, then install thermostat in cylinder head.
2. Position gasket and thermostat housing on cylinder head and install housing bolt and nut. Tighten to 14-19 ft lb.
3. Install upper radiator hose and connect EGO sensor electrical connector.
4. Connect engine ground strap to connector above housing, then the water thermos witch connector.
5. Install air intake tube and refill cooling system with 50/50 coolant/water mixture. Add coolant until radiator remains full.
6. Start engine and run until upper hose is warm. Check for leaks and refill if necessary.
7. Run engine for 12 minutes, then top off radiator. Securely install radiator cap with engine running.
8. Fill coolant recovery reservoir to the FULL HOT mark with 50/50 mixture of coolant and water.

Please let us know what happens.