The rust starts from the INSIDE of the door. Gravity causes moisture, dirt, salt, etc. to collects there and bubble out.
If Ford/Lincoln would coat the Steel, before they stamped and folded it together, it would last a lot longer. From what I can tell on my last car, all folded metal seems are bare metal underneath. The paint/corrosion coatings don't penetrate into the seams.
If you could pour or spray some sort of rust converting agent into the inner door frame, it might work it's way down and hopefully stop or slow the rust process.