How can one improve the recitation and memorization of the Noble Qur’an, especially in the absence of a specialized teacher and with advancing age?

The optimal way to perfect the recitation (tajweed (definition)) of the Quran is to present it to a skilled shaykh. If one is not available, traveling to seek one is religiously encouraged. If that is not possible, one can benefit from brothers who are knowledgeable and from recorded recitations of expert reciters. If a servant's intention is sincere, Allah will open doors of goodness for him.