Please post some images.
Re back flow, you need to understand the flow to see why it's occuring, and then whether it's effecting the result and/or area of interest.
Residuals may never converge for this type of problem. That's why we use monitor points (note POINT not area average on a surface). Have a look at the tutorials under Help and some of the courses under Learning (book icon left side of this page).
You are navigating away from the AIS Discovery experience