How can we help a father who prays, fasts, and gives zakat, but sometimes misses prayers outside of Ramadan?

Allah has commanded us to be good to our parents, and one of the greatest forms of goodness is to strive for their guidance. Your eagerness for your father's righteousness is a sign of good. You should advise him gently and wisely, send him da'wah messages that remind him of Allah, the Hereafter, and the status of prayer, and seek the help of some righteous relatives, while persistently supplicating for his guidance, for guidance is in Allah's hands. A Muslim should also be keen to reside in Muslim lands and avoid residing in the lands of the disbelievers.