Tighting the allen bolt on the top of your box won't remove any play from the system.
What it will do is place more pre-load on the sector shaft. (Requireing more effort from you to turn the wheel, more torque input from you that is).
It will not remove play, that is not it's design. Additionally, if you overtighten that bolt, you can break the sector shaft over time, leaving you in a potentially very bad situation going down the road.
I would avoid tightning that bolt.
YOu would only be masking the symtoms slightly, if at all
The ORD steering brace is an excellent upgrade, but it's more for preventing cracks in the frame than for reducing slop in the steering.
The most likely candidates for slop is the drag link, the tie-rod and the collapsable steering shaft.
Other high on the list are ball joints and wheel bearings.