Is it permissible to marry a married man whose wife causes him misery and uses witchcraft, and he is inclined to the questioner but withdraws?

The purpose of the Istikhara prayer is not to reveal the unseen. What you mentioned about that man's wife is not permissible. However, nothing he does permits you to fall into forbidden acts, such as loving a strange man, wishing for him to divorce his wife, and engaging in phone conversations with him, among other things. Therefore, we advise you to lessen this feeling and not to become attached to a man with whom you have no legitimate connection. If he wishes to marry you and proposes to you through your guardian, there is no sin upon you in marrying him if you deem him suitable in terms of religion and character. Otherwise, stay away from him and ask Allah to grant you a righteous husband.