The issue in the back is a different story. First of all, why is it even there? It's because when I made the "pin" group for the left breast, Poser's group editor helpfully selected an extra triangle for me that I could not see on account of it being blocked by LF2's entire body, and then I did not notice on account of not seeing it. In summary, all my fault. Apologies!

This is also in an area where the top tends to bunch up away from the skin, so the scaling approach will not necessarily work too well. My best suggestion at the moment for back views of the pinafore is to either completely clear out the constrained group or, for brave folks who speak group editor, remove the offending extra triangle. Also, turn on cloth self-intersection to minimize poke-through between the crossed straps. There's still some left in the render below, but I reckon that's in the ballpark where it can be either ignored (depending on the render) or fixed up post-simulation with the morph brush.

-- I'm not mad at you, just Westphalian.