Does the spout move in and out if you tug/push on it? If so, it was not secured with a drop ear or came loose over time. If it moves, I would open the wall on the other side and put in proper blocking to strap the pipe to. As for sealing, put a bead of silicone arounnd it, leaving a small gap at 6:00 O'Clock before you cinch up the pipe strap from behind.
Since it's been leaking, I would open up the wall from behind anyway to dry it out and mitigate any mold issue.
Are you sure the spout is threaded on? Some are held in place by a set screw on the bottom.