3) I experimented with the wrist a bit. I'd seen different approaches to the wrist in youtube clips, so I used mine as a "hinge" of sorts at the ends of casting strokes.
That is the problem. When you do that, you are driving the line into the ground behind you instead of flicking the line out straight behind you at an elevation higher than your head (and with enough directed momentum that it will completely straighten). You have to stop the rod - not your forearm- at the 1 oclock position.
When using the thumb on top grip, that means stopping your forearm on the backcast before it is even vertical.
I would again suggest tying the rod butt to your forearm, and practicing the backcast with no wrist at all. And I think that by shortening your stroke (stopping the rod like it hit a brick wall) up high, you will start getting some tight loops. Drop your right foot back (if right handed) so you can watch the backcast . Once you start getting tight loops, THEN you will know what people are talking about when they speak of "loading" the rod.
Another good way to practice is to stand with both legs spread on an imaginary line, and cast parallel to that imaginary line with the rod held horizontal. Then you can watch the entire loop formation both front and back. See what happens when you vary the stroke length. Slow the cast to where it barely straightens out both directions.
I would sign up for those lessons as soon as possible.
PS: Cracking the whip is a symptom of not pausing long enough to let the line straighten before casting the other direction or by slack due to a collapsing loop - nearly always caused by too much wrist at the end of the cast.
Your theory is not bunk. On casts to 80 feet or so the rod will not make any noise to speak of, though the line may whistle as it comes by.