Can Allah forgive my deceased father who did not pray, taking into account his kindness, good manners, praise of Allah, and charity, and is it possible that Allah has overlooked his shortcomings and granted him a good ending?

Neglecting prayer is a major sin. However, the majority of scholars consider someone who neglects prayer to be a Muslim. Therefore, it is permissible to supplicate for him and invoke mercy upon him, and his matter is with Allah. There is no harm in seeking forgiveness for your father and asking for mercy for him, for Allah's mercy encompasses all things. Any righteous deed you perform for your father, such as charity or reciting the Quran, will benefit him and its reward will reach him, by the permission of Allah.