Bank of America Corp’s $3 billion settlement with Fannie Mae and Freddie Mac may have brought New Year cheer to the bank’s stockholders, but now comes the hard part: settling far larger and thornier claims made by private mortgage investors. After Monday’s announcement, Bank of America still faces lawsuits stemming from $375 billion of mortgage-backed bonds. Compared with the deal with government-backed Fannie Mae and Freddie Mac, those legal claims will be far more difficult and costly and the latest settlement does not change that, according to legal experts and lawyers representing investors.