So I'm sure a few people are going to get a laugh out of this, but I didn't think it was fair to keep silent about it considering how I got a lot of honest and helpful advice in this thread.
Despite my numerous grumblings and ignorance, I might end up keeping the LG E6 over the KS8000. Ironically (or precisely because of), I reconsidered things after the LG sold on eBay for precisely the amount I paid for it, which would have been a big relief on my part.
In fairness, I probably wouldn't have come to this conclusion had I not experienced the KS8000 myself: after learning to dial down the contrast and embrace other presets besides Dynamic, I decided to apply what I learned back to the E6. Not only was I less anal about the screen not being ultra bright (since my eyes adjusted to the settings on the KS8000), but I didn't notice the ABL as much if at all. Fired up a few anime intros, played a little Transformers Devastation, basically anything with a lot of color and effects to see if the dimming was still frequent. About the only time I did notice was in Killing Floor 2 when using the flamethrower, but that might be mitigated further with a few other tweaks.
So I'm thinking of taking one more day and switching over from the KS8000 to the E6 to play some selected content, but so far I'm leaning heavily toward keeping the OLED: the benefits are hard to ignore, including stuff like FFXV and other 4K material looking noticeably more detailed, the pure blacks without a single hint of clouding, the passive 3D and even dolby vision (if that ever becomes a trend). Even the smaller size is a non-factor, as I noticed no difference in my living space between a 55' and a 60' TV.
Either way, I'll be making my choice by tomorrow. Since I have to stop by Best Buy anyway (to pick up my Zelda Amiibos), I'll either return the KS8000 or drop off the OLED at UPS.
What could help me in making a more definitive choice is nailing down some of the recommended settings on the OLED. I basically want to know what's best for HDR and non-HDR content, primarily for games but also movies. If I recall, max contrast and Dynamic Contrast at either medium or below are ideal for HDR content. I'm also wondering about Dynamic Color and especially Black Level: I was watching the newest Death Stranding trailer, and noticed that due to the Black Level, I couldn't make out Del Toro at all when he was inside the tunnel. But people tend to leave this on? If that's so then maybe another setting is conflicting with the picture.