How can a Muslim know that his uprightness is correct and that he is on the straight path, and what are the criteria for a righteous friend who can be relied upon to maintain this uprightness in a society where scholars of the Sunnah are few and innovations are many?

The correct methodology to follow in belief ('Aqeedah) and action is the methodology of Ahlus-Sunnah wal-Jama'ah (People of the Sunnah and the Community). Whoever follows the Qur'an and Sunnah with the understanding of the Salaf (pious predecessors) is upright, and whoever opposes them has gone astray. When there are few Sunni scholars, one should gather around those who are present and learn from them, or benefit from their audio recordings and books. One should enjoin good and forbid evil among their family, and avoid people of evil if possible. Companions who are diligent in prayer and attending gatherings of knowledge are the best to befriend. One must overlook any ignorance they may have, and they are not obliged to accept your opinion unless you are known for your knowledge.