What is the ruling of the Sharia regarding dealing with a disobedient mother who betrays her husband and practices sorcery, and does shunning her constitute an act of disobedience, especially since one of the shaykhs has issued a fatwa that disagreeing with her does not constitute disobedience?

If the questioner's claims about his mother are true, then she must sincerely repent from her illicit relationships and sorcery, and he must help and urge her to do so. The questioner erred by leaving the house, and his duty is to protect his family from the strange man. He must return home, expel that man, prevent his mother from meeting strangers, and, if necessary, restrain her. Filial piety towards the mother is obligatory despite her actions, and it is not permissible to disobey her. Rather, he should be kind and gentle with her, and try to change her environment and life.