Hi mayorted,
Vueling. Check out buying ticket online (cheapest if you can do it well in advance).
Look up their site and check out for best day of the week for it. I've used them 2 years in a row.
I've found the direct Vueling flight to CDG is really cheap, when done at right time ,whereas the long one via Barcelona can get quite pricy. Prices can change a lot when you're looking. Don't give up though. Just timing it.
Also, online if you know u will be checking in luggage, make sure you include that online and pay upfront. Doing this later can add a lot to cost of the whole flight .
Online -You can print your boarding pass at time of booking or do it from hotel in Santiago .
If you don't need to go to Paris, and you haven't locked in your main flight to Spain , check out flights to Madrid as starting point. Easier access on return
Buen Camino