trackman,
First, I will say that you were refering to Player B and not A in question #1. Robert's Rules Version 11,
BETTING AND RAISING
#12 To retain the right to act, a player must stop the action by calling "time" (or an equivalent word). Failure to stop the action before three or more players have acted behind you may cause you to lose the right to act.....There is more, but this covers your question. I thought that two players would be enough, but RR says otherwise.
Question's 2 and 3, I would rule Player A having a dead hand. The fact that a player bet on the next would indicate that the skipped player took far too long to stop the action.
Question #4. I guess that (based on RR's) his hand would still be live. However, IMO, I would not allow him any options other than check, or fold. I think the player picked-up too much information to allow him to bet. I also want to comment on the procedure that you described for reshuffling the turn. I will replace the "premature turn" with the proper river card, and then, if necessary, reshuffle the turn card into the stub, and place the "new river card" on the table.
Interesting topic.