Can outward religiosity be combined with inwardly committing forbidden acts, what is the extent of its impact on memorizing the Quran, is a person held accountable for entertaining ill thoughts in such a case, and how should one deal with this situation?

A person might mix good deeds with bad ones, and their inner self might contradict their outward appearance. The true state of hearts is known only to Allah. People should be dealt with based on their outward actions, without prying into their faults. One should think well of them and interpret their actions in the best possible light. If a slip occurs, it should be concealed unless there is a legitimate Shariah interest in revealing it. If they inform you of something bad about the woman without a legitimate Shariah interest, they are sinful, and you must rebuke them and defend the woman's honor. If they inform you for a legitimate interest (such as warning against evil), then take precaution without engaging in backbiting or ill-suspicion.