[DSPTurtle]

I wish all the plugs I changed looked that good. Nice clean burn. The ceramics don't look brown or discolored. Those look like they are fine. There is a contingent of people out there that do not like the four electrode Bosch plugs. They say it causes issues. Maybe you can try some plain jane Autolites or the single electrode Bosch and see if that helps.
If you had bad blowby those plugs would be much, much worse.
Have you tried switching the coil pack for Cyl 5 to another cylinder to see if the misfire follows? That is a BMW trick I learned since those things eat coil packs. Not even sure if you can do that on one of these motors (I am still learning my Mach) but that is the fastest, easiest and by far the cheapest diagnostic you can do.