MonoAccipiter

That's actually a game bug: https://fallout.wikia.com/wiki/Fallout:_New_Vegas_bugs#Barter_system_bugs
 
Check the first entry. Since it's from a mod vendor, you can try removing the plugin, saving, and re-adding the plugin, to force the vendor chest to reset.

My pack has been updated after I stopped maintaining F&L. Did you make sure to upgrade to CaliberX v5.0?

This is a weather "problem". The textures that emit light (like windows at night) do so by being connected to certain weather regions. Same with the windows in your screenshot. ILO won't make them any brighter, or less bright. It's not actually light, it's emittance, meaning that they glow, but they won't cast light on anything else. In any case, try dropping RWLE to the bottom of your load order. Also, there's a brightness setting in-game.
 
This is not a bug. It's how the mod is made. You can not like it – I don't like it – but there's no way to "fix" it.
 
This is FNV's default appearance...
 
Not sure how lighting problems would have anything to do with textures displayed at a distance. You're told not to deactivate it, because you shouldn't deactivate it.
 
Eyes: https://www.dropbox.com/s/vsnt4ne3jswj791/FCO%20EYE%20FIX.rar?dl=0

Load it after the Bashed Patch. Why do you have the TTW version of RWLE? 
 
Also, from the mod's description on FNVNexus:
 

Seems some of your problems are pretty common bugs as well: https://fallout.wikia.com/wiki/Hardcore_mode
 
According to the discussion page (click on the "Talk"-button) messing with the values (like PN does) or the timescale (like F&L recommends) can make vanilla bugs more pronounced, which I'm guessing is what happened here. Since you completed the playthrough, I'm gonna go ahead and hazard a guess at it being somewhat less noticeable when you hadn't played as long. The game gets decidedly less stable the longer you play because of more scripts running in the background, especially when mods are involved. Very many modders also use scripts that don't end themselves when done, which I can't imagine does the engine any favors in the long run.

Realized I didn't explain earlier, what you're experiencing is a crash at startup (hence why steam says it starts). Have you tried deleting your ini files? They're in "Documents\My Games\FalloutNV" usually. Steam won't replace those when you verify the cache IIRC, but if you start the game with them deleted, the launcher will make new ones.

Try setting it as some other key and see if the game registers it. Perhaps "Mouse Down" already serves some other function in the engine. I only use the two side-buttons on my mouse myself, one for activating iHUD and one for the companion menu (JIP C&C).

Try setting it as some other key and see if the game registers it. Perhaps "Mouse Down" already serves some other function in the engine. I only use the two side-buttons on my mouse myself, one for activating iHUD and one for the companion menu (JIP C&C).

I think those are just cells he left unfinished (but accessible) for no clear reason. I will probably disable the doors in the next update for NVInteriors Rewritten if I can just find out how to make my GECK load the NVInteriors BSA without crashing.

Yes. Advanced Recon Patches.esp replaces Advanced Recon Tech.esp.

It's neither. It is an issue with RWLE. Try moving the RWLE files further down in your load order manually and see if that helps. An ad hoc solution would be using the wait menu to wait for it to change the weather.

It's neither. It is an issue with RWLE. Try moving the RWLE files further down in your load order manually and see if that helps. An ad hoc solution would be using the wait menu to wait for it to change the weather.

Then put the FNVLODGen Resources folder above where the guide instructed you to place JIP NVSE. i.e. Before everything but the unmanaged folders and (potentially) the optimized texture folders.

Backup the MO directory and reinstall the game somewhere else through Steam, then paste in the MO directory again and reinstall the NVSE & ENB files (and whatever else you have installed outside of MO).

Well ENBoost should allow you to load some of the texture memory into your RAM instead of your VRAM, but your FPS is already pretty low, so you'd probably want to go back and see whether there are some more preformance friendly versions of the mods you've already installed, try avoiding STEP: Extended (sticking to STEP: Core) etcetera. There are also several mods in STEP that make the game look a lot nicer without taxing your resources too much, like Point the Way or 101Bugs.

From the first comment page of NVSR:
 
From looking over your mods I couldn't spot anything that seemed potentially unnerving, and I'm not entirely sure how either NVSR or NVAC works, but I'd guess NVAC is only supressing a problem with some other mod, making it appear (crash) later than it would without it.

If all you want him to do is use the special IA set, just copy over the entire IA record. IIRC The special loot flag decides what version of the set he spawns with, as the IASetTuliusBasic is another list, not an armor piece. Hope this helps.

Solved itself.