بسم الله الرحمن الرحيم
(1) We are sorry to tell you if someone has done black magic or not, as we do not know how to check it.
(2) If he fixed some amount for the treatment or he did not fix but you gave him on his demand or without demand then it was lawful to take and give the amount.
(3) If the Maulana Sahib is aware of the profession, you may trust him; there in no obstacle and if you do not trust him and avoid his treatment in future then too there is no harm.
(4)There is no harm in accepting the method which the Maulana has told you. You and your family members should read Surah al-Falaq and Sura al-Nas 3-3 times with durood 3-3 times before and after, and blow on your hands and pass your hands over your body. Also repeat the same practice before going to bed with wudhu on pure bed. It is hoped that this wazifah shall be of help to remove the evil effects, in-shaAllah.
Allah knows Best!
Darul Uloom Deoband