Two of the biggest things that help my safety game was learning the transfer of energy and the follow system.
Transferring energy: When you hit the cueball, its at 100%. If you hit the object ball with a full ball hit, you transfer 100% of the energy from the cueball to the object ball... stopping the cueball. A half ball hit transfers 50% energy and the cueball retains 50%... so they should travel the same distance. And so on... this should help with speed control.
Follow system: I personally find this system to be easier than trying to figure out 30 degrees or the peace sign thing. Understanding the exact path that the cueball will travel will dramatically help your safety game.
To use this system, find the line between the center of your object ball and center of the blocker ball (the solid red line). The red dot in the diagram on the object ball is your aim point. Aim directly for the red dot with follow. The cueball will follow directly to the blocker ball. From here, you just have to learn the proper speed and you can lock people up left and right. I know of a similar system for the exact path using draw... but draw is less predictable. But its setup a lot like this.
Try this out and your safety game should get much better quick. It did for me.