Sorry, I did not reply to your excellent and very helpful suggestions.
Here is what happened in the end: I called Airbnb aid line and there was a mediator who tried to solve the issue with my guest. The mediator was most helpful and very diplomatic. Unfortunately, my guest and I could not reach an agreement but I was able to ask him to leave the next day. The guest stayed at my house for free the previous month.
I was penalized for the remaining time of the original reservation (I could not advertise my place) and I spent the following year paying back the debt to Airbnb.
As a result, I lost the Superhost medal, and some income, but I gained experience (as soccer players like to say).
It was not a nice experience, but in the end I was able to have peace of mind and I learned a lot from it. No long-term rentals for me! 😄