Right, I went back to everything as in your description.
I have some head tracking, but the game image is moving, too. So although my view moves a bit, it doesn’t move as much as it should, it’s not 1:1, and the scene moves as well (but not as much as my head movement).
The 110° FOV is definitely too much. It looks far better at 90 for me. With 110, items close to me, such as cars, are stretched. This also makes the head movement look worse.
The vertical view is worse, though – it barely moves at all when I move my head up and down, and there is definite judder, with GUI overlays ghosting.
It’s definitely on Z_Adaptive, with Cinema off.
Separation = 1.00
Depth-weighting = 1.00
Depth of field = ON (off in game options)
Crystal Image = off
Aspect Ratio Correction = 1.1
Image zoom = 0.66 (I changed that, larger makes the zoomed-in effect worse)
Direct Mode Mirror Window = off
DM Async Renderer = on
DM Fluid Sync = off
Head Tracking = on
Sensitivity = 1.15
Roll = on
Inverts = off
Crouch/jump = off
I now have edge peek – that was my fault as I have a special profile for the game on my mouse and had MMB set to Flashlights.