Taking the train to Bilbao and catch a flight from there to Paris is a viable option.
Here are some other options:
Aena manages airports in Spain.
http://www.aena-aeropuertos.es/csee/Satellite/HomeAenaAeropuertos/en/Home.html
See Santiago SCQ, Barcelona BCN, and Vigo VGO.
Vueling was offering flights from Santiago to Paris CDG but currently that is not indicated on the Santiago website. It might be offered during summer season only.
Vueling and Ryan Air offer flights from Santiago to Barcelona. Air France has flights from Barcelona to Paris CDG.
Air France has flights from Vigo to Paris CDG.
Renfe provides train service to Irun where it connects to France SNCF TGV with service to Paris. (You could get off the train at Biarritz) Renfe also provides service to Barcelona where it connects to France SNCF TGV to Paris. The time to Paris via Irun or Barcelona is about the same.
Hermanos Ferrin (no website) provides bus service from Muxia to Santiago bus station.
Muxia Concello - See Noticias for link to bus schedule
http://www.concellomuxia.com/ca/web/index.php?dep=2&mod=not
Monbus provides bus service from Fisterra to Santiago bus station and Santiago bus station to Vigo bus station.
http://www.monbus.es/index2.htm
Santiago bus station
http://www.tussa.org/web/interior.php?txt=arbore_web5&lg=cas
Vigo bus station
http://vigobus.com/
Note: CDG is 25 km from Paris. Any accommodation near CDG Airport would be outside of any large city.