Fannish home owners, our homes, our repairs

My house is 110 years old, so it's something of a miracle that many of the walls and floors are still straight and at right angles with each other.

The door that's causing me problems is not one of those. It's original to the house, a panel door with cross-pieces at the top, middle, and bottom. It doesn't fit easily into its frame anymore because at some point the glue at the top joints came loose and it opened up some -- and then someone painted over it. So it's about an inch wider at the top than at the bottom. The doorframe is not square either. I'm not entirely sure that the doorframe isn't a structural element holding up the walls.

The latch and doorknob were part of a mortise lock assembly, and a piece of that broke.

So I have choices. Should I:
1) replace the mortise lock and plane the door to fit into the doorframe gracefully? (Possibly the least work.)
2) Buy a new door and cut it to the nonstandard and nonrectangular size?
3) Replace the door and doorframe. (Also possibly the least amount of work.)
4) Remove the door from the frame, strip the multiple layers of paint, knock it apart, and glue it back together the way it ought to be, install a new mortise lock, apply wood filler to the many and various dings, and try to rehang it?

I get the feeling that the last is the optimal solution, but also the most work.

Thoughts?