How can one deal with a father who commits forbidden acts and neglects his family duties, given that there are disclosures within the family about his behavior?

The duty of enjoining good and forbidding evil includes everyone capable of doing so. This father needs continuous advice, given with wisdom and good admonition, and the intercession of righteous people to guide him, along with prayers for his rectification. This father must repent before it is too late, for Allah accepts the repentance of a servant, no matter how great their sins, and His mercy is vast.