RK chain is a good quality product, in my experience.
I think that putting the original plug in the engine is your best bet. The heat range on both of those plugs is the same. The R indicates a resistor type plug and the S means it has some special construction. Otherwise, I think they serve virtually the same purpose. I imagine that the other plug was installed because it was available and the DR8ES was not.
Since you can't return the IMS pegs, I think you should grind the contact surfaces down a little bit more so the pegs function as usual. My 2 cents is that the bigger pegs are the first thing to upgrade to on a BW. It becomes really evident to me when I swap back and forth between bikes and I can stand up on one and not the other. The bigger pegs also don't fill up with ice as readily but that's not a feature appreciated by many people.
P.S. Fashion photos to follow soon