I can see you are very serious about this, but the short answer is to not overthink it. The long answer follows.
You should be measuring beyond where the shoulder bone connects with the arm, where your shoulder meets the fleshy upper part of your arm. You should be able to depress the top of the arm slightly where it arcs. No one wears their shirts with the seam riding up by the top of the shoulders, so if you are measuring near the nubs, you are doing it wrong. A shirt (I assume you were talking about shirts) seam should drape just slightly over that intersect, not sit flush on your shoulder bone, unless you want to feel a taut shirt all day. Yes, 16.5 is more akin to a size small or extra small, but everyone has different physiology.
You would be better served A) finding a shirt you like the fit on and measuring the fit from top shoulder seam to shoulder seam, laid flat, and working against that template; or B) going to a dry cleaner or tailor and asking them very nicely to help you. Perhaps you can think of a compelling reason to convince them.
Don't worry about yoke. And when self measuring, you should really have a third party measure you for an objective result.