Am I sinful if I do not pray behind an imam who errs in reciting the Qur’an, knowing that I recite the Qur’an better than him and he is older than me in age?

The imamate of someone who makes mistakes in recitation is valid if the error is not in Surat Al-Fatihah and does not change the meaning. There is no harm in following such an imam, even if the congregant recites better, as the imamate of a less proficient person is permissible. However, a Muslim must strive to perfect the recitation of the Quran, and it is from the Sunnah (definition) to prioritize the one who recites best and is most knowledgeable for the imamate.