Just moved into an old New England home and have some issues.

1. Steam heat throughout the house
2. 2 Zones (1 thermostat controls half of downstairs and the other controls the other half and then entire upstairs)
3. Oil boiler

Thermostat that controls the upstairs never accurately reads the temperature. We will go to bed and the it will be set at 62-65 and will come upstairs and it will be in the 50s (it is reading the temp downstairs and not registering upstairs at all). We have to raise the thermostat to 70 to make the boiler kick in. I will then open the air valve in the bedroom radiator to the highest number but the air valves will often hiss consistently and even spit out hot water. It is becoming virtually impossible to regulate temp in the house and I often will have to get up in the night and then turn the thermostat down because putting it to 68-70 will then make the room go to the mid 70s.

Any help/advice would be great! Thanks!