OK, so it should have been:
1. Ball touched by B in field of play, clock should start
2. Ball travels into EZ without an added force by B, so it's live, but in the EZ by force of the kick
3. B is free to bring it out, or down it in the EZ for a touchback (which it was).
OR
1. Ball wasn't touched by B in field of play
2. Ball should have been blown dead when it touched in the EZ
3. Clock never starts
What seems to have happened:
1. Ball was touched by B in field of play, but no official signalled it so clock didn't start
2. Ball was live in EZ, picked up by B and the clock starts
3. B tackled for a touchback, so clock stopped
While the final result was correct (touchback), the mechanics (and the clock) seem to have been butchered on this one.