I am tried now so I might ramble a bit here.
Your gas choice is good. All the oils you have ran are good too.
I personally do not like running yard equipment oil in my motorcycles or my MB.
Homelite makes good chainsaws, weed eaters, and leaf blowers but I have yet to see a good motorcycle made by them.
Well maby this one comes close, even though it's not Homelite:
Chainsaw-powered motorcycle startup - YouTube
I have one engine running a E3.10 and another running an NGK BPR6ES. Starting, smoothness, torque, and top speed are negligible between the two.
My opinion on the E3 plugs is they are a nice novelty item, like the Splitfire plugs.
The oils you have ran so far are good.
Stick with just one, run a brand new plug and you will get a better plug coloring.
You have ran so many different kinds of oil that I retract my suggestion of running a 1 step hotter plug
The deposits could very well be from trace residues mudding up on the surface of the plug. There have been too many variables in your choices of fuel blends to properly read the plug. Starting with a new plug also provides a clean "canvas" to color instead of a chemical coated old plug. Keep the old plug in your tool kit as a spare.
I run Maxima Castor 927, bought at the independent motorcycle shop down the street.