How can I repair a door surrounded by an older (100 yrs) home which is on such an angle that it can no longer be locked? The door has a dead-bolt but it is on such a strange...

The door has a dead-bolt but it is on such a strange angle that it can no longer be locked. Any ideas on how to repair this?
Before you undertake any drastic measures, try tightening the hinge screw, ESPECIALLY the top screw on the top hinge. If any screw just spins without tightening, replace it near a larger screw or repair the hole by glueing in a golf tee, next cutting off the excess.

In my experience, most lock alignment problems can be solved by ensure that the hinges are tightly screwed to the frame.
It sounds resembling the whole door frame is out of wack. The best thing would be to buy a fresh door in a frame and remove the old door and frame. Install the spanking new one ( be sure to leave the door in the frame as you bought it) making sure it is stratum and plumb. You will need to use shims to adjust the new door and frame. After it is solid stuff in the cracks with expandable foam and consent to it set over night then you can trim past its sell-by date the excess and put the trim back on the door frame, remove the wood pieces holding the door in the frame, install the lock and door knob and your done. Good Luck Sounds similar to the house needs to be jacked up and the foundation and beans need to be repaired. Something is wilting somewhere, and I doubt it's the door. I guess you could carefully take the jamb apart and reframe so that the first performance is square and put all the old stuff support. Or can you figure out where the door itself is out of square and plane that part of the pack off so the door closes.
Answers:    I only just moved from a house built in 1905 which I did a complete 10-yr renovation on. Not a single door in the house be lined up with the door knob serration.

BUT--to maintain the historical integrity of the house, don't remove the doors. It will lessen the value of your house. Here's what I did: I removed the dent and escutcheon plate that the deadlocks and door knobs latched into. I had a carpenter rip a unmarked facing on an angle to match the hanging angle of the door. Make it the entire plane of the door frame. After it is attached, paint it to match, and cut in a bright notch for the sliding mechanisms on the knob and locks.

If the difference on the door knob side is too great, you can rip a new angled facing on the hinge side and it won't be as noticeable.
you've probably already checked this, but the first thing I would do would be to examine the hinge and ensure they are tightened securely into the door frame and the door. If the screws are stripped out, this would rationale the door to hang at an angle. Well...To be honest: Without knowing how the house is constructed, it would be difficult for me to comment.
The general belief would be to level the foundation until all of the walls are plumb, and the floors are smooth. Yea..Right. Good luck with that.