Does the separation of FinCEN, and The Federal Reserve protect the integrity of a representative democracy?
Your understanding is wrong. FinCEN is a bureau of the United States Department of the Treasury. The director reports to the Secretary of the Treasury, who is appointed by the President and confirmed by the Senate. 

Further, the Federal Reserve system is also a government entity. It was established under the Federal Reserve Act. The Federal Reserve Board of Governors, which supervises the Federal Reserve Banks, is an independent agency of the federal government. Its members are appointed by the President, with the advice and consent of the Senate. The system's structure was deliberately designed by Congress to grant it independence in its conduct of monetary policy, with the intent of minimizing political interference in monetary policy. However, this independence was granted and is maintained via democratic consensus.