What is incumbent upon one who has recited the Qur’an while in a state of ritual impurity (junub) and has not performed ghusl for a long time, and will the reward for his recitation be lost?

Sincere repentance to Allah Almighty is obligatory for abandoning prayer and masturbation. The majority of scholars hold that all missed prayers must be made up. As for reading the Qur'an, its reward is not lost if the questioner was unaware of the ruling.