I wouldn't add a border -- just a nice solid binding-- a grey would be nice.
If you use drapery rod hardware, it will stand out from the wall -- which is fine if that's what you want. Alternatively, you can use a piece of flat trim molding from the hardware store (often pre-painted) and run that inside your hanging sleeve. The trim piece can either rest on small picture hooks, or you can use fine nails through holes in the trim. This gives you a wall hanging that lies flush against the wall.
Consider putting hanging sleeve on either end, so that you can rotate the quilt and avoid having it warp or have sun exposure in only certain areas.
As for batting -- I think it's good to do trials with your intended batting and the actual fabric scraps. It's a great opportunity to practice your quilting ideas. Then wash the samples and see which one holds up best. Use your samples for throw pillows, coasters, table runners, pet bed -- whatever would be handy to coordinate in the room where you're hanging this.
I think it will look great -- post photos so we can see it in place!