You might want to maximise your opportunities to see Europe from ground level rather than above the clouds, and minimise your time hanging about in airports and incidentally your carbon emissions.
I am sure there are trains or long distance buses which would get you from Santiago to Toulouse with a change or two in somewhere interesting.
Bilbao on the north coast of Spain springs to mind, with its modern art museum, and closeness to Guernica (horrific bombing atrocity by Luftwaffe in 1937, famous painting by Picasso), or Barcelona (with famous Gaudi architecture).
From Bilbao I would expect to get a bus or train to somewhere like Bayonne, and change there for Toulouse. From Barcelona you would be travelling up the mediteranean coast into France, via Coullioure (small French port where Matisse did a lot of painting) and perhaps change at Perpignan for Toulouse. I have travelled on a train south to Coullioure and enjoyed views of lagoons with flamingos.
If you have the time you could research all sorts of places between Santiago and Toulouse to see what fits best with your enthusiasms. (You might detect a bit of early 20 Century art in mine! But then I like the early medieval as well!)
But whatever, it will be worth booking as early as possible to ge the best prices. I am just being offered two singles fares on the train from Paris to Limoges for 32 euros! With no extras for luggage, checking in, paying with a card, getting a bus or taxi to and from the airport or having to wait around in a hot dry airport in a queue with no chairs to sit on, with a full bladder. (Who can I mean? clue ANIRARY is the anagram. But they ARE cheap.)
Other people are quicker than I am with finding routes and times on the web, but for trains I would recommend
http://www.seat61.com. Or ask Ivar to help with your bookings (see below)!