Wow, amazing (and rather greedy).

When I was young and used to put up with 'standard economy class' long haul travel, I used to sleep with my seat fully upright frequently because I felt guilty about reclining because it clearly reduced the space for the person behind me. I had a bad neck for a long time from a whiplash injury, but at no time did I get any extra injury from it. A bit of extra sore neck for quite a while? Yes. My head jerking about sleeping? Yes. $600,000 worth of injury? No.

If he was that uncomfortable, why did he carry on sleeping in that position, and apparently without using a pillow etc?

Was he forced to sleep in that position? No, in my opinion, because he was not forced to sleep.

Did he ask to be re-seated for a while (e.g. in a cabin crew jumpseat, which I have to say there is no recline)?

Besides, I hear a lot of LCCs fly around for 4 hours or so without any seat recline whatsoever. Would he sue for that, I wonder?