I’m sorry for your frustration. I know the feeling.
The light samples are made by Lightmass, so you need to rebuild lighting to add the new ones. They are also constrained by your Lightmass Importance Volume, so make sure you have one and it is the right size for the best results.
Did you increase the number of Volume Lighting Samples? That should be pretty easy to tell in that visualize mode after building.
I ran some tests on that Character Indirect Lighting Volume. Turns out it doesn’t add an extra concentration of lighting samples, it just forces Lightmass to build them in areas that it would ordinarily deem unnecessary, since it only builds them at player height.
But it sounds like the samples aren’t your problem if you’ve got an object sitting right on top of one and it’s still super bright. The only other tweak to rule out the volume samples is to crank up your light settings if you haven’t already. I’ve got Bounces at 100, Indirect quality at 6+, Volume placement scale at 0.5, and Production build quality. Maybe the samples just aren’t good at getting accurate measurements without the refinement of the indirect quality or something. But I suspect this isn’t the case.
Like I said, I had this issue only when a pesky dynamic (or stationary) light was sneaking in through a backface. I would turn off all dynamic lights and see what happens after rebuilding lighting for good measure. I don’t know what your room setup looks like, but make sure there are thick blockers and everything is set to cast dynamic shadows. In my experience with sky lights, they tend to create an ambient light for things that are supposedly out of their view, so turn down its intensity or disable it. Turn down or disable your directional light as well and rebuild.
After reading your other posts, it sounds like you are doing everything right, so I’m running out of advice.