I use the 155 cover 3 F@G almost exactly the same, except for the DT. I do not put him in contain. You would not believe the numbner of sacks you can get with just him rushing.
Keep the DT in his assigned rush, against all 5 linemen. When you see him getting close or the QB moving off to one side and the DT is on that side. Quickly hit B on 360, roll off the blocker and get the sack.