How can one deal with a father with whom communication is difficult, and who neither appreciates nor relies on his son, knowing that the son strives hard to please his Lord and his parents despite this treatment?

You have no option but to endure your father's harm, and to consistently obey, honor, and be good to him. He is your gate to Paradise. The Prophet, peace and blessings be upon him, said: "The parent is the middle gate of Paradise. So if you wish, abandon that gate or preserve it." Try gently and wisely to get closer to him, show affection, consult him in your affairs, and give him gifts, for the Prophet, peace and blessings be upon him, said: "Exchange gifts, and you will love each other."

As for your mother, continue to communicate with her, reassure her, and bring joy to her, and the greatest of that is for her to see your relationship with your father as good.