Yeah, I learned this the hard way. I made the same mistakes OP made: A super-demanding client wanted pictures, wanted me to hurry because he needed the pictures urgently. Then ruined my vacation by phoning me the whole time. Then, suddenly, it was not urgent anymore but demanded photos that are not my style, demanded changes and then more changes. Then, finally, I finished, sent the bill. Last thing I heard from him that he is sick and broke, his company is down the drain and he doesn't want to pay anyway. I think he never even intended to pay because every time I mentioned additional costs he told me they don't matter. Well...

I will go through default action (is that the right word? What I mean is that I make the demands for payment official and an excecutor will be assigned to the task. It's not that expensive). But full court proceedings - no. I guess I have to cut my losses, learn from the experience and move on.

And next time no work until I get an advance and no delivery until I get paid in full. Ugh.