Well, I don't know how it works in France, but in the U.S. if somebody defrauds several people, once he gets caught he has to make restitution to everyone in the order in which he defaulted/defrauded. So if you found him and tried to sue or file criminal fraud charges everyone else that he already owed money would be able to get in line in front of you, and there's a good chance he'd be out of money by the time it was your turn to sue. I'm not a lawyer, so this all may be wrong but this is my understanding of our system. Hopefully a real lawyer will pop in here and tell us how far off I am.
Of course, you're in France, so I have no idea how it would work there. If you can get a free consultation with a lawyer it might be worth it to find out if you have any options, but I kind of remember you saying you'd already been told it wouldn't be worth it. So your best bet is probably to just call this "a learning experience" and cut your losses. And really, even if you found him, sued him and won, if he doesn't have the money that doesn't really do you much good anyway.
I'm glad your house is finally coming together. The timing sure sucked, though.
I like how you refer to expenses in terms of the vacations they could have paid for. I used to be the same way, but with alcohol instead of vacations. Last year my car needed a new water pump and when the mechanic told me how much it would cost I said,"Are you crazy? I could buy 4 cases of whiskey for that much!"
Why do your shoulders get so stiff? Have you seen a doctor about that?
In closing, and maybe off topic, you're a very impressive woman. In the last 3 months we've covered your friend/stalker, stress at work, swollen glands/hypochondria, home maintenance, and the death of your father. It's like I'm watching a reality show of a woman whose life, for all practical purposes, should be falling apart. But you seem to have an uncanny ability to take everything in stride and keep being proactive even as things keep getting worse and worse. I wish I knew more people like you. If you ever do get a chance to take some time to yourself and relax and unwind, be sure to give yourself a nice pat on the back. You're probably the most resilient person I know.