Also, the light from headlamp seems too focused. It should be much more diffused to light up surroundings, without passing through the walls ;) of course.

I can confirm.
If you are in first person view, go prone and then try to roll left or right, the first person view is not rotated to reflect the roll, instead it is translated as if the character was crawling sideways (strafing). Third person view however shows correct roll animation. This has been present in ALL versions for me since beginning of early access on Steam.

Flashlight shines through walls as well in structures. I noticed it in the police station (one with the jail) and those rows of personal garages. It could be structure related or just present for all structures. Not sure.

Agree. I have a mid range PC and framerate drops to 1-3 in Cherno and Highrise residential area between Cherno and Balota. It is not a constant drop, it goes back when you enter the building. Most likely it has to do with large building models (or large number of them) being viewed from Outside, possibly related to visible interiors.
I am not knowledgeable in graphics but could it be because interiors do not have low res version of textures for distance viewing?

Confirm. was crawling for 20 minutes today with broken legs. Then got disconnected. Reconnected (different server) and my legs were just fine.