Open the door just enough to get it off the latch and try pulling up from the rear bottom edge. It's pretty heavy so it takes a bit of force to move it. If you open it any more you won't be able to test for play since you'll be applying that force in the wrong direction. Also, take a look at the panel gap between the front and rear door to see if it's equal throughout, and compare the level of the lower window trim between the 2 windows. Mine is very clearly lower than the rear door if you look at the trim.

 

Yeah, that's always bothered me about mine, except it's with the rear driver side door. It's visibly lower, and if you open the door, you can see where it's rubbed on top of the wheel well.

 

So the door lining up has kinda become a "maybe later" issue... I took the car to a shop that my wifes, friends, husband owns. I told him about the vibration in the center of the car that was mostly noticeable slowing down from 60ish. He put the car up on a lift and grabbed a ball joint on the driver side front. Said it was bad and said that was the problem. I said that was weird being that it was in the center of the car. I had him go ahead and replace the ball joint, raise the car up a couple inches, and align the front and rear. The car rides a lot better now... Problem isn't fixed...

 

I'm not surprised it isn't fixeed. I've had a lot of control arm/ball joint problems but never felt them comoing up from the drive shaft tunnel. Put in neutral and slow down like younusually do. If there is no vibration, the drive shaft theory looks a lot better.