I'm not a Diana trigger expert but pretty sure that the 45 will have sported a two stage trigger?
Do you know if it has the T01 trigger fitted? If so, it most definitely will be a two-stage unit and a very good one at that, once properly adjusted. That rear screw should not be loctited. Adjustment wise (assuming both adjusters are working) it wants setting up so that the first stage is doing most of the work, allowing for a lighter, crisper second stage release. I can't remember now off hand as to exactly how to adjust, but seem to remember that the front screw will adjust the first stage and the rear one the second, but await someone else jumping in to properly advise.