A fix for that mold would be to remove the sprue plate screw and drill all the way through and tap from the sprue plate side for an allen head set screw that would go in first under the sprue plate screw. You'd have to put it in upside down so the allen wrench could be inserted from the other side of the block. Once the sprue plate is adjusted tighten the set screw down. It won't damage the threads because it will be against the tip of the sprue plate screw. After the threads are cut for the new set screw the threads would have to repaired for the sprue plate screw of course. Better to do it after drilling and tapping the new set screw threads.
Does that make sense without pics?
I don't use loctite on the set screws because it loosens before the mold is up to temp.