Philosophically, if there have been numerous "pump-fakes" during this run, doesn't it make sense to rule this a fumble.....?
Additionally, 2-31-2 Note says: "Prior to releasing the pass, if the potential passer is contacted, and the ball is released, it is a forward pass if his arm was moving forward on contact".
With that said, 2-32-11 defines a passer as: "a player who throws a legal forward pass".
In this instance, isn't A1 only a runner who fumbled the ball?
A's ball at the B25 if the live ball spearing penalty by B (who is ejected in any event) is declined; OR depending on where the fumble occurred, that could be the basic spot for the enforcement of the spearing foul - if it were to A's advantage.
No foul by A. It's like an illegal kick - which is treated like a fumble.