PPRUNE Fan,
Don't get hung up on the word trim. That word to me means the place where the stick is put to make the helo stay right where you want it. If you are flying at 80 knots, the cyclic is forward of where it is in a hover, and a bit to the right, in most western helos. If you then push full right pedal so the aircraft flips around in yaw and goes backwards at 80 knots, do you think the aircraft will just stay level in pitch and roll? Of course not. Because the cyclic is in the "wrong" place for the new position, it will cause the aircraft to roll and pitch a lot.
For small angles of yaw, this misplaced cyclic will tend to cause positive dihedral. The effect at very low speeds like 60 knots and below, is small, and easily over shadowed by the effects of the fuselage, horizontal tail and even that fin on the roof. That might be why your experiment in your helo shows no positive dihedral. What helo? What speed? In an S76 at 140 knots, yaw is more powerful that lateral cyclic in creating a bank! In an S-76 at 40 knots, it will not bank, just swap ends.
I don't have the time to answer each of your points, but you are basically incorrect if you think that pushing pedal does not cause a turn, if the wings are level. (This is not the basic subject here, as I contend some bank will happen, and you have to supress it with cyclic). If the ball is out and the wings are level, you are turning, that's why the ball is out! I won't go thru a tome here. If you disgree, then tell us why the ball is not centered.