chistletoe,
Wow -- you've jumped in with both feet! Sounds like you're ready for the challenges: the next year or so will be tough, but after it all you'll have some great stories to tell, and you'll really know the Northeast, which is probably my favorite part of Brazil, having lived almost three years northeast of you in Sergipe. Let's get into your questions.
Yes, if you marry under Brazilian law (whether in the cartório or a religious marriage with civil effect), it should be recognized in the US. Marriage in the US is a state, not a Federal matter, so I would recommend contacting the responsible authority in the last state where you lived, or even better where you still have a home if you have one, to find out how to register your Brazilian marriage if you want to be doubly sure. In many states, that will be the County Clerk.
Unfortunately, you'll have to file your US taxes as "Married, filing Separately", unless you can get your wife an ITIN, an Individual Taxpayer Identification Number, which you can only do in the US. If you have a lawyer or tax preparer in the US, maybe that person can help you.
The full-service US Consulate General responsible for your region of Brazil is in Rio de Janeiro. There is no US Consulate in Salvador, but there is a Consular Agency ( we have the same situation here in Manaus). The Consular Agency only provides services to US citizens, not consular services to Brazilians. They may be able to advise you on how Brazilian and US law interact in the areas that concern you. Here's their contact information:
https://br.usembassy.gov/u-s-citizen-se … formation/
You won't be able to open a bank account until you have a CRNM. It looks like the Federal Police office that you need to contact about it is in Barreiras -- see page 9 of this document:
http://www.pf.gov.br/servicos-pf/imigra … de2013.pdf
Although it's difficult, it's essential to get your CRNM if you want to live in Brazil. You'll also need to get a CPF, but you should be able to get that at the Receita Federal in Bom Jesus da Lapa. Until you have those, your only convenient source of cash will be your US debit card, preferably at the ATMs at the Banco do Brasil and other banks. Try to avoid ATMs in places like stores, since they're easier for thieves to scam than the ones in bank lobbies.
I don't know anything about buying rural property, so I won't guess and risk misleading you. I hope that someone with experience in the area will chime in.
For professionals, if you don't know anyone else yet, but you and/or Maria belong to a church, I'd ask your priest or pastor whether they know anyone. Otherwise,
The Order of Advocates of Brazil (equivalent to the Bar Association in the US) has an office in Bom Jesus da Lapa. You may be able to get recommendations for lawyers to interview there:
http://www.oab-ba.org.br/oab/subsecoes/ … us-da-lapa
For accountants, try a Google search on "Escritórios de Contabilidade Bom Jesus da Lapa". In both cases, it comes down to shoe leather: interviewing professionals until you meet someone who seems competent and interested, and that you can work with.
If you have more questions, please post them. All the best!