There's also some "speed of the game" issues he has to deal with. The SEC is fast, but not NFL fast.Just going off of my own experience of playing free in HS...
Rambo is not necessarily taking the wrong angles - at least initially. Whenever a RB or WR breaks into the secondary, the free needs to keep the player coming at him from making that cut. In other words, you need to continue to force them to the outside and square your hips in that direction. Yes, you give up another eight to ten yards or so, but you don't allow the cut to happen and have the offensive player taking it to the house.
Rambo will learn that lesson and he will be fine. Every free learns it at some point.