If the spinner is breaking where the screws go in that hold it together you're overtightening them. Just snug them down until the seam is tight and then stop.

Your starter issue could be an over primed engine, but that's not the only thing. An old starter cone will tend to spin since it doesn't grip as well as a new one does. Trying to start your engine when it's up against the compression is another common cause. Turn the prop backwards until you feel the compression, then hit it with the starter. Also another tip: keep your starter cone clean. Just a little bit of dust is enough to make a ring if the cone slips, and any liquid will cause cause it to slip.