Is it permissible for someone who has forgotten a verse other than Al-Fatiha, or is confused about recalling it and no one is there to help him, to recite it if its wording becomes clear to him, or is it better to move on to the next verse?

If you doubt a word in the Qur'an, it is not permissible to recite it with doubt. However, if you are strongly inclined towards a particular word, there is no harm in reciting what you believe to be correct. Indeed, the jurist Ibn Hajar al-Makki mentioned that it is not permissible to recite with doubt until one is strongly inclined towards the correct word. You may omit the doubtful passage and move on to another, or stop reciting and perform rukūʿ (bowing). The matter is flexible.