I admire your positivism!

On some of your questions i have some answers. This is from so long ago that there is not a written record. We can’t really compare these people to a modern day or even historical folk. It would take 2000 years for people to describe who lived in these areas, by then they were called gauls by the Romans.

However there is a point made by antropologists that the basque language is a remnant:

Archeologists are unsure whether Western Europe saw a Mesolithic immigration. Populations speaking non-Indo-European languages are obvious candidates for Mesolithic remnants. The Vascons (Basques) of the Pyrenees present the strongest case, since their language is related to none other in the world, and the Basque population has a distinct genetic profile.

Almost none of the settlements are standing, however in the Dordogne region of France (where the famous Lascaux cave paintings are from) have sites where people have lived 17000 years ago.