In some respects this strikes me as quite inefficient.
If Spain is your destination, why drive there from Paris? If for some reason you need/want to start the trip in Paris, why not grab a cheap flight from Paris to a city in Spain, and go from there? Also, why drive all the way back (3 days?) from southern Spain to Paris? Why not fly open jaws (into Paris, and home from Madrid or Lisbon), or at least save the time/expense of driving back to Paris and catch a cheap flight?
The other thing that strikes me as problematic is that you seem to be headed for and conentrating mostly on the great (old) cities -- places where a car is just an expensive headache.
If I were doing a trip to these places (and I'm about to do one that's somewhat similar...) I'd fly between the longer distances, take trains to go between most of the cities, and only rent a car for those few, specific places where a car makes the most sense (there are places where a car is much more convenient -- Normandy, and parts of Portugal, for example -- but I don't think I see many of those on your list).
Now, for some folks there's some appeal to the long drive through the countryside - I get that (but you say you don't want to spend all your time in a car). But if your time is limited and you hope to cover a lot of ground and see a lot of cities, driving is often (usually?) not the best way to go IMHO. I may be missing some good reasons you've chosen to go that way, but if it were me, I'd take a step back and consider other, more efficient ways to get from one place to another, that involved less driving, and more trains (and maybe more flights).
Just my 2 eurocents.