In other words, if you want to prove that your father is having an affair, so as to put your mother in a favorable position when the court decides that your parents are divorced, you must pay attention to the legality of your evidence collection.
I'll tell you briefly from the aspect of legality.
First of all, checking your father's QQ chat record is an invasion of personal privacy. Even if evidence is obtained, it is illegal to obtain evidence, and the court will not accept it.
Secondly, most of your photos are of that woman and your father, which only shows that they are often together, which is not direct evidence, that is, it cannot directly prove that your father had a relationship with that woman (sexual relationship).
Third, your recording is legal evidence, I think, but the place where your father beat your mother should be your home. If it is in your home, you recorded it, which is legal and valid evidence, which can directly prove that your father has domestic violence and belongs to the wrong party in divorce proceedings.
Finally, if you want to get legal and direct evidence, you'd better install a camera in your bedroom to induce your father and that woman to have sex in this place and get video evidence. This kind of evidence is legal and can directly prove that your father has an affair.
Finally, I just want to say that this kind of thing is a misfortune in your life. I hope to take good care of your mother in the future, especially psychologically, and let her get rid of the shadow of your father's extramarital affairs as soon as possible.