Is it permissible to perform Istikhara for divorce before marriage, and is it legislated in this case despite the husband not being accepted even though he is deemed suitable in the eyes of the family?

Istikhara is performed for permissible matters. The default ruling is that a wife is forbidden from seeking divorce without a valid Shar'i reason. However, if you are uncomfortable and fear neglecting his rights, you have the right to seek a divorce or khul' (divorce initiated by the wife in exchange for compensation), and you may perform Istikhara regarding this. Your family is not allowed to compel you to stay with him, and you are not obliged to obey them in this matter, because obedience is only in what is recognized as good. If the husband is righteous and you can endure with him to please your parents and show them piety, then do so. A guardian is not permitted to force a mature virgin into marriage with someone she dislikes, and she has the right to seek annulment of the marriage if she was coerced into it.