There are several simple things: radiator fluid could be low, thermostat could be bad, partially plugged heater core (less likely), bad heater control system-electrical.
35 psi is a little on the high end for tire pressure. Would recommend going with 32 psi. Remember that the manufacturer sometimes recommends things to reduce maintenance costs (longer times between oil changes for example) or improve mileage (higher tire pressure or using 5W20 motor oil), that...