Arms Don't Swing & Character Stretched

It looks like Right Arm under it has “Arm” marked as independent. I don’t think that is what you want. Try leaving Right Arm as independent but the child Arm layer remove the “+” / crown from that layer. You want independence only on layers that should move separately. E.g. the arm wants to swing beside the body so should be independent, but the hand should not be independent as it should move etc with the arm. So Arm being independent inside Right Arm is a bit strange And might be causing the problem.

There are probably multiple issues, but one strange one I notice is the arm origin is not green, as in it is not attached to its parent. The Attach Type is auto however (correct). There is also no yellow outline around the arm - just the blue bounding box. Could you click on the Body layer above the arm in rigging, and include that screenshot as well? Also, in the scene window, try holding down ALT and clicking the refresh button at the bottom left (two arrows in a circle). That flushes some internal caches Just in case.

CH requires everything in a layer to be contiguous. You could try setting the Contour setting to see if that helps. Its almost like some bits of artwork ended up in the wrong layers, confusing CH.