Yes, "to see" is stative. It is very, very rare to use progressive/continuous (-ing) tenses with stative verbs, but we *do* do it occasionally, usually when we want to show that one person experiences something in a way that other people wouldn't. For example: "You keep telling me you hate me, but as long as you keep looking at me with love in your eyes, I'll keep *hearing* everything you say as "I love you.""

"My man" = my husband/boyfriend in this context (possibly my friend) "was seeing the ball like a melon" = he now had enough practice at the sport (spent enough time doing it) that he was able to see/hit/catch the ball very easily. To explain, a ball is typically quite small, e.g. a baseball. Once the person is good at the sport, they can see the ball easier, and it's idiomatically described as a melon, which is obviously quite large :)