First get a CO2 and CO monitor.
I'd suggest one of those heater units that screw onto the top of a 20lb propane tank,if there is now way you can switch to a wood stove.Again, another reason for a canvas wall ten t vs a nylon one. You wil be much warmer with les heat.
I bought one of the vent free Blue Flame propane heaters from Northern Tool,on sale for $100.Oxygen sensor,auto shut off. adjustable from 0 to 30,000 BTU's. Much more efficient than a catalytic heater.
If you are from low elevation, not being able to sleep,might be from the altitude,not the cold air, unles syou have COPD or asthma.You might try a scarf or? over your mouth and nose,so the air is somewhat warmed up before you breath it.
