I would follow advice from jkhill0.

Your timing might not point out the fact that you should have been promoted. I've got guys in my year group who will have their second look this April. Some may have made it last April but haven't pinned.

As far as the attitude of not making the cut, if you were any other year group, this wouldn't have been an issue.

If asked why I was getting out, I would respond that you were looking for more stability in life and wanted to part ways with military life. It was good experience but....