Did the achievement glitch on your account?
Did you start out on SuperSoldier Difficulty?
Did the Veteran 3/7 achievement unlock?
Not sure what that means but veteran unlocked and everything is at 7/7
Did you access the tutorial from a new game or through the menu?
Through New Game
Prior to campaign completion, did you replay missions through mission select?
no, started the game off on SS diff.
If it didn't unlock initially, how did you finally get it to pop?
Haven't yet, just beat AC at the end and tried playing first level and tutorial to unlock it (both on SS as well)
Did you press the X button to skip cutscenes either at the end of a chapter or during a mission briefing?
Nope, i only hit x to skip a cutscene once during my playthrough and it was on accident