Well done, Todd, and nicely clarified. The only thing is your point 4b: the K&M 23550 bar already comes with two thread adapters that screw onto the thumb screws on the bar to lock them in place. At least the K&M bar did when I bought one. Then again, having a few more thread adapters on hand, especially for just another couple dollars, is not a bad thing. 
Gracias!
The weird thing about that is it lists the same bar, same part number differently on various sites.
So I just went to the actual K&M site and got the actual # which is 23550 and shows it with 3/8" mic screws.
The pic on the B&H site acttually shows the mic bar flipped over so you only see the mic holder screw knobs not the threading.
The only thing consistent about this is the inconsistency