Check the ring for broken socket fingers where the adjuster screws snap in, it may just need a gentle push to re-engage otherwise you will need a new mount, they are available at summit racing for around 40 bucks
That crack looks to me like it's on the lower alternator mount bracket. The bracket is made of magnesium and cannot be repaired, you will need to find a replacement. I have seen these online even billet ones I believe out of Arizona