Re: Mistaken Charge at PK
The relevant bit is this, but its not in the 2018 book only the 2017.
(e) If the opposing team infringes while the kick is being taken but the kick at goal is successful,
the goal stands. A further penalty is not awarded for the infringement.
This bit is in 2018 though (my bold) and I would include charging as obstructing the kicker.
15. The opposing team may not do anything to delay the kick
or obstruct the kicker,
including intentionally taking, throwing or kicking the ball out of reach of the team
awarded the penalty.
Sanction: Second penalty or free-kick, 10 metres in front of the
original mark. The second penalty or free-kick must not be taken before the referee has
made the mark.
There is nothing about time and PK's, but since the law allows a conversion to be declined (to speed up the restart) I would take that to mean the clock doesn't stop during the PK, retake process. There is certainly nothing in the Time Law to support stopping the clock, but then neither is there anything about stopping the clock for scrum resets and that happens all the time at top level.
If you thought the opposing team had deliberately contrived to delay the kick, in order to run the clock down to the end of the game, you could of course award a PK for deliberately offending, which would be a PK restart if the kick was successful.