You can check Access Newspaper Archives (I have access through both my regional genealogy society and a public library card)
Each has something different. I recently did a speech where I utilized a lot of newspaper research. Although many of the sites overlapped, I did find something different on each one.
There's also the Portuguese-American Digital Newspaper collection (most are in the Portuguese language) that UMass Dartmouth digitized. They have MA, CA, and HI papers:
As to narrowing down when your uncle came to Brazil, you'll have to utilize Brazilian records to create a timeline. Many here on this list research Brazil as well and may have ideas for you.
Researching: São Miguel island: Vila Franca, Ponta Garca, Ribeira Quente, Ribeira das Tainhas, Achada