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You make no mention of the mileage on the car.
When is the last time you replaced the PCV?
What viscosity oil are you using?
If you are using, as an example, 5W30 try 10W30.
Use a high mileage oil that typically contains an additive for seals such as found on the valves.
From your description a guess would be a bad electrical connection but whether external or internal to the radio is hard to say, You mention instrumentation also, what exactly happens to the instruments?
when cold is the coolant bottle at the proper level?
when the engine is fully warmed up does the upper radiator hose feel very warm to the touch?
the heater control valve would be located in one of the two heater core hoses. If it sticks closed no heat.
solve the P0106 and P0506 codes and the P00C7 should also go away
P0106 DTC Code - MAP / Baro Pressure Circuit Range/Performance Problem
P0506 Idle Air Control System RPM Lower Than Expected - DTC Code