From the Shoulder measurements, you are right at the high end for the Small, and Low end for the medium. Likewise for the waist. Only way to really know is to try one on. Are you near a Zeagle dealer that could help to fit you with one?
The Ranger, and many other Zeagle BCDs allow changes of some components to get a better fit. I believe right now, only the Scout and Covert don't offer this, but some of the upcoming jacket styles (Grace, Focus, Base, Resort, & Element) may be more standard sizing as opposed to PFS (Personal Fit Sizing). Any of the BCs with PFS will allow you to swap out shoulder or waist sections. So you could get a BC with Medium shoulder & Small waist or vice-versa.
I had to do this with my Stiletto. The large was too big, but the medium had the cummerbund too high. My dive shop took a Medium BC, and swapped the Medium shoulder with a Large shoulder, and it fit perfectly.
I'm thinking you are more in the medium range. The medium will give your room to grow in the waist section, which most of us do as we age, but should still fit your shoulders. The Zeagle back-inflates are made to be worn a little lower than a standard jacket BC, so it should fit.
Or, if the pricing on the small is significantly different, then order that, but you may need to swap out either, or both of the sections to medium, which would probably eat up any savings unless the seller lets you exchange them.