>>414007747
Oh I see how the bumps are being made now. It's the vertex normals. If recalculating normals and setting from faces doesn't work then you're going to have to either bake normals from like a cylinder onto it or manually shift every vert so there aren't any high or low points (don't do this). You can also retopo it.
As for making a new UV map you can mark seams along the seams of the shirt to make panels and then unwrap it and bake the old textures onto the new map.