Bag is not attached to arm, it keeps moving

Hi. The bag is attached to b__R_ThighTwist__, which is not the right bone at all. I'm not sure which is the right bone or if there should be multiple, but try attaching it to b__Spine1__ and then check how it works

You need to delete uv_0 and uv_1, then rename UVMap to uv_0. Then vertex paint the mesh with black so that it does not morph

The normals on the yellow rope are flipped