I don't see cutting himself or beaten by bro on purpose(anger mentiond). He loves Dave even if he seemed to be biggest dick in the world. Dave is just a horny boy, and bro is having hard times to refuse to play with him

So, Dave is definitely a masochist and degradee on top of that
But only for bro. Dave visualize too much when bro presses him against anything. Fear of what bro could do to him drives him nuts

Thank you!