Was this door damaged by the minivan or in another accident?
No the door has never been damaged.
Maybe it's because my car has been built on Monday the 13th 2008, I'm not kidding!

By the way I've been to my favorite paintshop.
The guy told me that such damage occurs when the two shells haven't been joined properly (water can leak between the two shells and they start to rust).
They've repaired a lot Ford cars with the same problem.
Got an offer about 250$ for the repair which includes removing the rust and damaged sealing, applying a new sealing, new paint job and spraying wax on the inside of the door.
Only thing they asked me to do is to remove the door and bring it to the shop.
Additionally I'm thinking about spraying some wax on the inside of the passenger door (saw some spray cans on Amazon).
Hope that's as easy as it looks.