I've heard about this "glitch" that people refer to, which will allow one to pick any chapter of the game to play, which might well make it easier for me to finish the game on tougher difficulty settings . . . how might I do this, and how does it work?
There is a well-documented feature of the game that has been dubbed "the glitch," but is, in fact, an intended feature to the game, once you have completed one play-through on any difficulty. This link goes into that feature, in great detail (one of the posts in the thread even has a Youtube video link, showing how to accomplish this, which you may find extremely helpful):