Weird cooling on my 84 D150
I've had heater hoses freeze up on me when in a situation similar to yours and I had to temporarily get by with added water. Even though I added antifreeze later to get back to having a correct mix, it took weeks before a proper thaw allowed the new coolant through the heater hoses. That would explain a lack of heat inside the cab. If there is observable flow in the radiator then I'd suspect a faulty temperature gauge combined with frozen heater hoses/heater core.
