Your heater control valve is either failed (likely) or the control cable has come loose (unlikely).

I do not understand the "poor air quality" you speak of so a better description my help. Is it a smell? Lack of air movement? What vshicle(s) are you comparing it to?

I mis the fresh air vent front early 240's that was in the toe kick area but I still would not consider the ventilation poor if the blower motor is working and all the vents are open.