Is a son considered disobedient if he abandons his father who neglects prayer and commits grave sins, and claims he is a Muslim because he recites the two testimonies of faith and does not worship idols, and threatened his son with reporting him, knowing that the son is committed to his prayers and considers his father an infidel?

Your father is in grave danger due to the major sins he commits, the greatest of which is abandoning prayer. However, his commission of these major sins does not negate the obligation of honoring him. Rather, you must accompany him with kindness. Honoring him entails advising him gently and with good admonition, seeking help from people of knowledge and goodness if necessary, and striving to supplicate for him in his absence. Your kindness towards him will be more effective in influencing him than mere admonitions. Beware of looking down upon him; instead, feel Allah's favor upon you and be merciful towards him.