No the President has not amended it. Don't ask me why? Some poltical handler thinks folk won't except it. No Congress does not have to approve or radify it. The 1942 case set all of this in motion.
From the 1942 SCOTUS decision: "It is unnecessary for present purposes to determine to what extent the President as Commander in Chief has constitutional power to create military commissions without the support of Congressional legislation. For here Congress has authorized trial of offenses against the law of war before such commissions."