Set frames to unlimited and get back to me.  This makes all the difference in the world for me with complex add-ons around airports.

To be safe I ditch all AI.  Use the global setting of "High" and crank down the water no higher than Mid 1.x  That would be my recommended starting point and see how that works.

I don't care for Lens Flare or Light Bloom (usually).  No a/c shadows.  No land or boat traffic.

I haven't found much of a difference with or without the cabin, so I keep it.  By the time you want to play with wx radar, you should be away from the airport and getting smooth FPS.  

I am using nHancer and keep my computer defragged with O&O.

I never have intractable problems with stuttering, and I will tell you the standard I use.   If I can taxi and look from one side the other of the vc smoothly, i.e. without jerking, then it is acceptable to me.

I have a Dell XPS 430 2.5 Core 2 Quad with 6 MB RAM & a GeForce 9800GT.  At KATL I'm good in the 767.

There are too many variables to guarantee everyone is going to have the same experience.  All I can tell you is how I set up and get smooth frames with the 767.  You're going to have to make your own trial and error experiments.

This IS one of the most FPS-challenging airplanes around.  It's like a big budget picture that cost a lot, but at least you can look at the screen and say it's all up there.  You should NOT expect the same performance as some other payware a/c.  That is not unusual at all.  The question is whether you can run it smoothly with some acceptable configuration on your system.