As you've already pointed out, it really varies so much store to store and by the person. At 158 I was a pretty solid 8/10 and my goal was a 6/8 too. With a medium frame I figured I needed to be between 137-145 to be that size. However, now, having gained some weight (and a good portion of it being muscle), I'm a pretty solid 8/10 (10 in more dress clothes) and 20lbs heavier. The last time I was at this weight I was a pretty solid size 12. It varies so much depending on body composition.
Also, at my lowest weight, I had one random, size 12 dress, that I loved but agonized over a little because I couldn't believe it was a size 12. Which was silly in retrospect, but it just goes to show you!
I think 152, based on your current weight and size, probably sounds like a solid endgame for now. You'll definitely reevaluate as you go.