Frustrating furnace issue

Put some heat by the propane bottle and regulator. Couple 100w incandescent bulbs would do.

Sounds like it's a fuel issue. The stove and fridge use less gas then the furnace. Try putting a drop light under the pressure regulator outside at the tanks and keep the plastic cover over ever thing if you still have it, this will keep the regulator and tank valve from freezsing up. It could well be freezing up due to the volume of fuel the furnace is drawing.

It never got above forty degrees in the trailer though. And when i shut the furnace off and switch between bottles it works again for about an hour then i do the same thing switch bottles and run it about an hour again. Also the fan continually runs until i turn it off and the igniter snaps ceaselessly

A safety issue. When the furnace reaches the set temp the flame stops but the fan continues to run until the combustion chamber cools enough to be safe. Likely nothing wrong and it is working correctly

You're correct i just joined, due to the issues issues I'm having. It's an atwood furnace in an 06 Dutchman 31 foot that i recently bought and haven't been able to find a model number due to faded stickers.

You just joined. Remember, for accurate help you need to always post Year/Brand/Model of RV AND the brand and model of the appliance.
IF the Furnace runs and heats for 1 to 2 hours, odds are it has reached temp and it goes into a cool down cycle. There is a Hi Limit switch to prevent the burner chamber from being TOO HOT after the furnace reaches temp. This cool down can last from 5 to 10 minutes and then the furnace fan motor shuts off. IF the HI limit fails to operate, the fan will stay ON until you switch it off at the tstat. This is the most common cause of your type problem. Doug