Praise be to Allah, the Lord of the Worlds; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.
This brother should be patient and be pleased with what Allah has predestined for him. The misfortune that has befallen him is probably a mercy from Allah; the trials wipe out sins and upgrades the person's status, making him come closer to Allah.
A Muslim should not give up hope of Allah's soothing Mercy, and should not be suspicious about other Muslims, let alone being their enemy just because he was cheated by one of them.
In addition to this, he should fulfill the rights of his mother, by being kind and dutiful to her and establishing good relations with her. The right of the parents is great, so please refer to Fatwa: 83443 and 82254.
He should also fulfill the right of his wife and family. The Prophet (Sallallahu Alaihi wa Sallam) said: "The best among yourselves, are the people who are the best to their wives (and family) and I am the best to my wives." [Reported by Tirmizi, Ibn Majah and others]
If he is angry and upset, then he has to read the Qur'an and remember Allah a lot.
The remembrance of Allah enlivens the soul and makes our hearts righteous. He has also to read the stories of the patient and righteous people. He may also consult a doctor.
Allah knows best.