If the experience of a British friend of mine with a Columbian wife but living in Spain is anything to go by, he has and continues to have constant hassle with visas and they have to visit Madrid rather regularly to renew one thing after another. Not impossible but do prepare for long waiting times. Good luck.

As for flights, check out the search sites such as Rumbo: Vuelos, Hoteles, Viajes y Vacaciones which gives an idea of costs, routes and airlines. Looks like at least 1200 euros return and 2 stops from Davao to Madrid.