Being dogs are domesticated and fed by humans, this isn't really "Darwinism" nor "Natural Selection." Also, if you pair up breedings, then you are referring to artificial selection.
As far as calling them Brazilian Bullmastiffs, that is fine. I however, as would most people that by using the name "BrazilianBandogge" that you consider the ability to engage important (as it would also be with the old style bullmastiffs). However, it is reasonable for people to ask you to validate this. There are several ways to do this. You can use various tittles, or you can use photos and videos. Whatever floats your boat. Good luck.