I have read one biography of Paul, but for the life of me can't remember the title. I think it said that his relationship with his mother, Catherine the Great seemed to go up and down in later years. Sometimes it was worse, but sometimes it was better. I think that's interesting, and rings true. But, after her death, he was indeed against her. Maybe if he was ever nice to her, it was because he wanted the position of heir no matter what, although Catherine would never have entertained the idea of making someone else her heir. Catherine, on her side as well, never really tried to have any sort of bond with him- she thought other things more important, although she used him to justify her taking the throne. Both of them were to blame for their less than satisfactory relationship. However, circumstances of how he was born and raised are most to blame, in my opinion.
As for his reputation, he gets over shadowed by the reign of his mother, ( naturally), and also by the reign of his son, which seemed much more normal than his. He wasn't as bad as claimed, something you are surprised to find out when you read a biography of him. Most books about his mother make him look bad. He was a complex person, and it is easier to condemn him than to attempt to understand him. He, in my opinion, doesn't deserve to be condemned. Russia was an mixed up country to rule, as much as his own behaviour was said to be to blame for the state of the country and court when he died. He seemed to try to be like his purported father, Peter III too much, because he was trying to escape his mother's shadow, and embrace what he thought of as his paternal legacy. That did not make him popular, anymore than Peter III had been popular, and in fact most likely less so. I am of the opinion that if Paul had a different background and upbringing in particular, he would have been a good ruler. He wasn't inherently unstable, it was more the circumstances of his life that shaped his destiny in a not always good way, and made him act in ways that did not make him look good. His motivation was usually not bad.