"you can just follow the windshield line and see it gradually get smaller toward the driver side. "
What does the window slant have to do with the door closure? There is a lot of pieces that could be adjusted.
How did you come to your 3/4 inch off measurement?
That window piller post is the toughest most solid piece in the car. Your not going to move it IMO with a bottle jack. Everyplace else on the car would start to give before that would. If you are correct about it being off I would wonder if it was due to damage or factory tolerance.
It may be worth your time to locate a competent old school body man for a second opinion.
