Do you believe Bro was under the influence of Lil Cal? I don't believe so because of his shades? Since eyes are the door way to the soul, maybe the Striders closed that connection off with their shades so they couldn't be influenced?
I don’t believe he was being controlled, but he spent a lifetime with Cal so I doubt he escaped influence entirely even with his shades. Being influenced by Cal didn’t cause his abusive tendencies as Dirk has been shown to possess a few of them himself and his Cal was empty, but it likely did enhance them and make them worse. However, even if Cal influenced his behavior that still doesn’t excuse the abuse he put Dave through.