I am confused by your instructions!!! You say most Ruger shoot best with the screws loose, but then you say to tighten the front and back screw tight and just snug on the middle screw.
You want to have them all loose at first. Then tighten them in the order I suggested. The screws need to be very tight. But if you don't start with them all loose it could be putting stress on the action as you tighten them.
The angled action screw Ruger uses can work, but it works different. By tightening the front screw 1st, it pulls the gun down into the stock snugly. Then you tighten the others. If you don't loosen the others fist, you will just be getting the screw tight, but with the other screws already tightened they will not allow the action to move down and back into the stock properly.