Hi Silver,
Sorry to see these problems. I just went out to check my Northstar and I have a very different door on my propane compartment. This is made be Elixer.
There's a shield above the top hinge and a bottom lip that goes all the way across.
Note there's also a vent hole that exits out the bottom of the camper, though that's not part of the door. I'm sure the vent is intended to allow any escaped propane to safely exit the compartment but any water that did intrude would also exit there. I wonder if allowing a path for any propane leakage to escape was the reason for the gap at the bottom of your door?
May give you some ideas for your repair/rebuild.
