Can’t answer your mortgage question, sorry. But as you’re considering a house purchase in Portugal…
Portugal residential real-estate can be a bit “wild west.” I’m not sure if there’s any accreditation required, and our Agent (in Madeira) has told us of various dirty tricks like stealing each other’s clients, Agents not crediting other Agents who introduced buyers to them, etc. If you’re familiar with the relative transparency and orderliness of the MLS® or the National Association of REALTORS® in Canada/US, Portugal doesn’t have that. So beware!
There’s been a few other relevant threads on NG - careful as some of the posts are obviously Agents masquerading as helpful souls…