How can a Muslim know if he has fallen short in his duty towards his deceased mother, and if she was pleased with him before her death, given that he sees visions of his mother smiling and she has told him things that have already happened?

Filial piety is among the best acts of obedience, especially in old age. Indeed, whoever finds both his parents, or one of them, in old age, and then does not enter Paradise, has been disappointed and lost. If you fulfilled your mother's right to kindness and benevolence, then you will not be harmed by your father's harsh treatment of her. Knowing her satisfaction comes from what you used to do for her and the signs of contentment she showed you. As for visions and dreams, nothing is built upon them, but they can be glad tidings if they are pleasant.