Is the inquirer or his father sinful if he stops reading from some of the many copies of the Qur’an available in the house, and is reading a single verse from the Qur’an sufficient so that it is not considered abandoned?

There is no harm in having a number of Qur'ans in the house, and there is no sin upon you for limiting your reading to your personal Qur'an. It is more appropriate for your father to give away any excess beyond your needs to someone who can benefit from them.