To be honest with you, I do not know what would help at this juncture. The Thor I am familiar with and this one are very different.
Ordinarily I would suggest allowing him to work out the excess 'grumpiness' on a good fight, but I suppose in this circumstance that would be the opposite of beneficial, given that he is trying to avoid that... and, of course, given the lack of reasonably worthwhile yet... disposable opponents.
Perhaps just attempting to take his mind off the issue would suffice. I would advise not allowing him access to his communication device until morning at the earliest.
Pranks would be the last thing I would suggest when he is already in a foul mood, you need not worry.