I have tent camped in mid January every year for years, here in SC. You can safely heat a large tent and be comfortable. It has become a sport for me...this year we had a night with a low temp of 26 degrees.
Inside temp - 74!
I used one of the round kerosene heaters on full blast and a small electric heater that had a thermostat to fine tune the temps!
You can do it if, I repeat if...you have a tent tall enough that the heat disipates before melting the roof. Smaller tents, I would recommend electric radiant heaters.
Be sure to put a carpet on the floor, both for comfort and safety. Be safe, test the rig out in advance when you arent depending on it to be asleep in.
Generally tents leak enough air so that CO isnt a problem, but a detector is a great idea. I had to block about 90% of my roof screen vent area to hold in heat.