Does that screw in the bottom of the grip of a revolver control the amount of force the hammer will deliver to a primer? If so, which direction on a Smith increases the blow?

That screw holds the spring in, it will effect hammer force, but it is to be turned all the way in.
Good luck!

Some people loosen the strain screw to lighten trigger pull weight. This also lightens hammer fall and often results in light hits.

In a Smith the single action pull is determined by the rebound spring.
Good luck!