Given the importance of the mental aspect of playing pool, that's an entirely legitimate reason to use a closed bridge. I say use whichever works best for you for whatever reason - there's probably no overriding benefit to knowing the "science" of this.
Yes. At least to the point where you don't hit as low as you intend.
A snug closed bridge allows the preferred grip - OK.
My closed bridge has no daylight around the stick. Just like Mosconi taught me.
I copied LoreeJon's loop in my closed bridge because it's loose and relaxed but the way the loop leans, it still secures the cue stick, which for me is the best of both worlds.
I recall she started to market a hand held bridging aid that was subsequently outlawed by some pigheaded sanctioning board. (sry BJ) People with small hands/arthritic hands/no hands need such tools already.
Except as described above by several of us, those (lower level, if you like) players who wiggle and/or use aggressive strokes find the closed bridge restricts unneeded cue movement.
The reason to restrict most unneeded cue movement (movement after tip/ball contact) is psychological - it's distracting, but doesn't affect the shot itself. Hiding stroke errors that move the cue before contact is another reason, I guess...
Yours, on the other hand, is simply incorrect. I didn't say anything about what "all billiards players" do or think; only about the physical realities of open & closed bridges.
I don't know anything about a hand-held bridge aid and you haven't provided enough information for anyone to agree with you or not as to the ruling of the legality of it.
Slomo videos of tip/ball collisions show that the shaft/tip reacts identically with an open or closed bridge until after the cue ball is gone.
It was a small, handheld, rectangular piece of plastic that somehow worked with a standard bridge. It was advertised in Billiards Digest many years ago. You'll have to ask her about it. I don't even remember the name of it. Anyway the point was there should be bridging aids for more elevation, shooting from the rail, even a post for "freehand" jumps and Masses.
Wait... I thought you were a scientist. You aren't? You're unfamiliar with experiments in a controlled environment? At this point it's still your opinion.
No - and if you want to get familiar with some, you might start here with Dr. Dave's Billiard Digest article (and related videos) from 2017:
I was dumbfounded the first time I noticed Neil and Judd doing this -- pulling up slightly with the shooting hand, flexing the cue against the chest and down onto the bridge hand. The stroke doesn't just look like they hit it hard -- it looks spring-loaded, unleashed, all the while maintaining the accurate strike on the cue ball!
For some of them the flex is against the chin, or so it seems.
The pendulum stroke will arc the tip downward. The ridiculous stick taper compensates for this. I think the tiny tip might might also help in pointing the impact where it is most efficient.