Well, it is nowhere written, that -exThreads=4 is wrong. Even that the table doesn't contain description for that count. I don't have time right now, but I will try all variants of the setting. For me it looks like that if I set up the geometry extra thread (which from what I get is the -exThreads=4 setting) it stops running. Is it so, that the file operations thread has to be turned on for the other threads to run? If so, it might be the problem.

I tried to delete the startup parameters one after another and I found out that without the -exThreads=4 parameters it works. Means that with "-nosplash -noPause -world=empty -cpuCount=4 -maxmem=8192 -maxvram=1024" it works fine (as it seems right now)

PS. Actually with the exThreads=3 it runs as well. (I just found out that the exThreads should be less then cpuCount) I wonder why it didnt fail on other missions.

I passed both the RPTs before the successful game cache validation and after. I did it I hope all right (I even run it as admin this time).
I will pass you my startup parameters if it can be any help: -nosplash -noPause -world=empty -cpuCount=4 -exThreads=4 -maxmem=8192 -maxvram=1024

Well - there still is possible way how to achieve it without your computers to blow up while rendering 3 squads with flashlights. It might be possible to do a per-vertex shading. It will probably look terrible and your computers will just grill, not explode, but you will have your dynamic cast shadows. I mean - it might be possible to prerender the shading for static lights (which is practically useless because it is always possible that some building will blow up and so) but you can not have per pixel dynamic cast shadows on landscape like Altis is. Not yet, not now. (I strongly believe in voxelization and stuff used in unreal engine 4 which might bring some changes into ways things are rendered, but its still kind of new stuff)

Your machine would probably implode and made a blackhole in night PVP 20v20 mission with headlights. Well there still are some limitations to the graphical pipelines. This is possible only in engines handling small areas with small numbers of lights.