Is it permissible to supplicate for an unknown young man who is an innovator, asking for his guidance to the Sunnah and that Allah makes him my husband, after admiring his appearance and averting my gaze from him?

You have succeeded in lowering your gaze from the young man you admire, and this is the Islamic duty. There is no harm in supplicating for his guidance and his turning away from falsehood. It is permissible to supplicate for marriage to him after his guidance. If that is facilitated, then praise be to Allah. Otherwise, do not burden yourself with him, and ask Allah for a righteous husband. Seek help from trustworthy individuals in searching for a husband.