hiii heres my 2 videos with retopolization in them, it doesnt really explain it but then again, you already know the basics
http://www.youtube.com/watch?v=Wtr4w5PtU7k
http://www.youtube.com/watch?v=IgB41xJxUg0
tell me if it helps–
and yea your edgeflow looks fine- seems like u pulled it off nicely. i think the problem with the back is that theres not enough polys in that one spot to project the details right… the deformed polys are right over the point with 5 intersecting lines, that should usually be avoided, especially when u have details everywhere. you can always sculpt that new mesh, and retopologize again. You can even decimate ur model a few times, sculpt some new details and then retopologize http://www.pixologic.com/zbrush/features/decimation/