I didn't read this whole thread. I do have a portable propane heater but, I do not use it when I am sleeping. I fire it up before I go to bed. And I Make Sure That I have A Window Slightly Cracked. I get it up to about 75 degrees f in the camper. Then I shut it off, shut the window, and go to bed with blankets next to me that I can pull over myself as it get colder during the night.
I have a 30 year old furnace. I took it out, cleaned it, inspected it, and I feel that it's safe. Probably safer then a newer and cheaper made one really.