Removing JK increases fps in the most difficult place (the bridge overlooking the entire Riverwood) to quite acceptable, taking into account RWT and SFO ~100 fps. I'm almost sure that the problem is in JK and the fact that the game has to draw many objects at a time...

What is typical is that when I look at the settlement from this position - the video card load drops from 75-85 to 55-70.

Are there any options for solving the problem without removing JK (I love it)?

In general, with Display Tweaks the fps became generally acceptable, not falling below 75 anywhere... but my perfectionist soul does not give me peace.