Dear Ana,
Both Mathias Correia's previous wife, Ursula da Ponte, and Sebastiana de Medeiros Costa's previous husband, Afonso Correia, were buried in Furnas (back then belonging to the parish of Maia), so you may find their marriages in the book entitled “Famílias do Vale das Furnas” by Luís Miguel Rodrigues Martins.
Please bear in mind that the book contains a couple of mistakes (hope I won't get in trouble for saying this), but it's a great reference to guide you in the right direction/ parish. They might have gotten married to their previous spouses in neighbouring parishes.
Best regards,
Carlos