1994 Oldsmobile Cutlass Engine Overheating

My 1994 Oldsmobile Cutlass Supreme, milage 245,000 is overheating. I have replaced the radiator, water pump, thermostat, hoses, serpentine belt, and a second time the thermostat. This all started with my temperature guage fluctuating significantly until the vehicle warmed sufficiently, then the guage would normalize. While the guage fluctuated the heater inside the cab wouldn't work when the temperature was hotter than normal. This last time, after replacing the thermostat a second time, the guage remained in the red zone on the temperature guage. Both upper and lower hoses were hot and highly pressurized, yet the car was overheating, and no heat was coming out of the heater inside the cab.
It is almost as if the thermostat is closed. Besides driving the car into a pond (the thought has crossed my mind), what can I do?
Note: Earlier today I sent in a credit card payment of $10 to be applied to this question (transaction ID: 2222471542), thank you!