You've pretty much got it Hlbly. The pebbles (tap,tap,tap) are kind of a gentle rumble if you will and a bit more rapid because airflow is still moving somewhat efficiently across the wing, as it progresses the rocks (thump,thump, thump) are an indication of more airflow disturbance, and the boulders(bang, bang, bang) are the last warning before the stall is fully developed and lift is lost. As far as frequency goes, probably more in the beginning and less at the end game.
The stick movement and force or load are dependant on the configuration. High speed, accelerated stall, responsive stick input, honk the stick back, she digs in and pebbles,rocks, boulders progress rapidly (frequency?). A fully configure landing stall with flaps 50, this stick is somewhat sloppier than above and the pebbles, rocks, and boulders develop more slowly (frequency?). Again, the Mustang is very honest and predictable. But, like ANY airplane, a pilot can get himself in a square corner and have areal bad outcome.
Earl mentioned the deer on the runway scenario and what he experienced. I was taught to perform a go around with partial increase in power, flaps to 30 (less drag and more lift), trim, and then flaps 20, trim, flaps 10, trim, flaps up, trim, landing gear up, trim. See the constant need for trim with configuration change? My instructor said that most Mustang go around accidents result in a balked landing or bounce while trying to save the landing. In the process, airspeed drops off, the safety margin between flying speed and stall speed closes, panic reaction occurs, a yank on the stick occurs creating a stall and immediate application of full power results in what Earl described below; the stall occurs and the high power setting creates a torque roll, and over she goes onto her back with no altitude to recover. Earl needed 800 feet to get back under control in that situation. At only a few feet above the runway, it's all history from there.
Your power steering is another good analogy to describe use of trim. In trim...power steering, out of trim.....power steering has failed.