My well fitting jeans measure 16" from edge to edge - straight across.
What about for the thigh and knee measurements, should I size down for that?
My well fitting jeans measure 10.75" for the thigh (which is actually pretty tight).
It is such a shame, they are freaking nice jeans.
Next time you decide to order online. Measure a reference pair (a pair that fits you well and has the same fit).
You can't size down on parts of a jean. All measurements make a fit to what of is. Sizing down on one region will make all other parts smaller too. Some of these regions are not easy to stretch, like thighs for instance.