There’s two parameters - light responsiveness and master brightness. They’re effectively the same thing and I should probably remove one of them. Try adjusting both of them down until it looks right. You’re getting weird results though, for sure.
The range of the dot product should be 0-1 as it’s simply a UV sampler, that’s what the code you unhooked does. Whatever you’re getting now isn’t the intended result. The -1 to 1 will definitely cause the LUT to loop across the scope of the phong result, giving you light patches in parts that should be dark, or what you linked in the last image.
Is there any chance you can migrate the barrel, materials and light setup to a blank project and send it? I want to see what’s going on there.
Ah, sorry…the final picture didn’t show it, but I did clamp the result from 0 to 1. Basically, backfaces (which were getting dot product results from -1 to 0) were being turned into numbers from 0 to 0.5 with that re-scaling of the range, and depending on the light properties/LUT/intensity/blah blah blah, could show some level of light.
By clamping those numbers directly (and not doing the + 1, / 2 thing), all results from -1 to 0 were being turned into 0, which is zero light, which is what I wanted.
I can still try to export the project but things are working exactly like I want right now! The barrel and material used in that test shot are entirely unmodified from the Sample map pack, I just added a red point light. (It was in a separate project that didn’t use my custom modifications, which mostly have to do with how it gathers lights.)
Oh I’m with you. In that case good work, I’ll apply that to the asset. 
If you have any suggestions for improving light gathering or a particular use case that you think is good, feel free to share it.
Where is the document or tutorial, ??