Thought I'd use my nifty wank-tracking skillz and take a crack at this.
The Arc Reactor of the Mk VI Iron Man suit has an output is above 10 gigawatts, or 10 gigajoules per second. Scaling off the Mk I's Arc Reactor, which has a 3 GW output and 15 minute duration, which was stated on-screen in the first Iron Man movie and only improved...
The total capacity of the Mk VI is 10 GJ/sec * 15 min * 60 sec/min = 9000 GJ = 9 TJ
Thor overloads the suit to 475%.
Now, this doesn't tell us much without assuming how full Tony was at the time.
Since Iron Man's RT was 63%, the answer to the question is clear.
475-63=412. The energy is 4.12 * 9 TJ = 37.08 TJ. 37.08 TJ * 1 kt/4.184 TJ = 8.86 kilotons
The power is 37.08 TJ * 1 TW/TJ/sec * 1/4.27 sec = 8.68 TW lightning which is 2.07 kilotons each second