Yep that will work fine and yes the ground will be fine anywhere on the chassis. You won’t have to add a fuse on the wire since the lighting circuit is already protected at the fuse block but you can if you want it can’t hurt.
Juts be sure your tapping the running light and not the brake light.
I would use fine sandpaper rather than a wire wheel . .Honda serial numbers aren't very deeply stamped on the older machines and the metal of that crossbar is quite soft. A wire wheel might "smudge" the numbers. I learned that the hard way when I did mine .