Problems with rigging and the mirroring therein

So, first off, I was wondering if there was a way to make the bones stay inside the arm, because they seem to want to display a bend more than they’re bending the actual arm, like this:

The second problem is with the mirroring. When the bend in the picture above is on the left side of the doll, this first picture is what’s going on with the right hand, and then the second one is with no rotation on the left arm but with the same sort of bend set to the arm that’s being weird. I’ve triple-checked all the bone-names, so I’m stuck. Help please!

looks for me that the vertices of the thumb are assigned to some part of the left arm?

might have 2 armature modifiers on the mesh, one sitting there normally and the other waiting for you to make real. only need one.

also if theres a mirror on the mesh then should be simply mirroring the other side? you sure the mirror is even on?