The "bold parts".
What I meant is that, with AC, there will be a current flowing all the time that there is an AC arc this will mean Power is dissipated all the time an arc exists. The current will be charging / discharging your body every cycle during the connection process. This arc will burn you. I have seen a movie of the operation in which a man holds an 'earthing' wand for some time with lots of sparking, until he actually dares to touch the conductors.
For a one-off discharge (raindrop landing or charged man), the current flows just once so not much energy transfer. For live working on a DC power line, I think the situation would be more like the raindrop situation.
The red part.
When you get down to it, it's always energy that counts. Whatever the rate of transfer of energy (i.e. power), there is always a limit to the amount of damage you can do with 1J of energy. To achieve anything at all, there is usually some lower limit to the actual power needed in order to make this change. That's a general principle.
I seem to remember the tables for electrical risk have more or less the same 'current times time' value over quite a range. Below a certain current you can go on for ever but, at higher currents, there's another factor and your body is more susceptible.
I have just one reservation about the way you use the formula. That formula was not, I suspect, produced for Capacitor Discharge safety but for exposure to Mains Supply hazard. Do you have a better reference than "as far as I can recall" haha? Let's see if we can thrash this out.
btw 'as far as I can recall', the Leyden Jars on a Whimshurst machine (such as we were allowed to use at School in the 60s - but no longer) could kill you on a bad (/good) day. That could give us a figure to go on.