The door should close unless:
- it has been warped or twisted by force
- it has had new seal installed badly
- there is something else blocking it
If best option is the seal, you can try replacing seal, but make sure there are no other obstructions or warping first..
As for power source, freezer and refrigerator are cooled by same ammonia piping and coolant, so if one works the other should, unless there is clog or problem with cooling unit (search above for "cooling unit" and "fridge" or "refrigerator"). Some trailers had 12V
electrical system, rather than 110V power for electrical operation. The 12V
heater will drain the battery and put out less heat (heating the fluid produces cooling..) than 110V AC powered heater. Propane operation uses 12V
only to power the control cuircuit board, and gas flame provides heat for coolant.