Hi Carlos,
Do you want to hire someone to verify that the Francisco you found is your Francisco? Or you want to hire someone to build the tree back from the Francisco that you found?
Sao Miguel had about 60 some churches in the 1700s. I'm sure there is more than one Francisco born to a João Fonseca in the mid-1700s in São Miguel.
If Brazil does not have inbound passenger lists and his marriage did not state both of his parents, you may have to use DNA to figure this out. It will be a bit of challenge. That time period is difficult.
Cheri Mello
Listowner, Azores-Gen
Researching: São Miguel island: Vila Franca, Ponta Garca, Ribeira Quente, Ribeira das Tainhas, Achada