He needs more obedience training. He has hit that awkward teenage stage, where he is challenging everyone for dominance. How much training has he had?

You may want to try some simple behavior training right away. When your stepson is going to come over, make sure you have the dog with you, on a leash. If he starts toward you stepson, tug the leash and redirect his attention toward you. Once your stepson is inside, and the dog is calm, the stepson can then go get a small treat, and work with asking the dog to sit, and them giving him the treat, and praising him if he takes it gently. Any sign of aggression, and no treat. If possible, have the stepson take him for a walk when he visits, just so they get acquainted, and the dog gets used to him. Then you can work on socialization with other young men. Will the dog play with a ball? Is there any game the stepson could play with the dog after all the initial greeting and entering is calm and peaceful?

Peeing in the ouch is definitely "marking" behavior, and cannot be tolerated. First clean it thoroughly with a good enzymatic cleaner, so not scent of the pee remains. Then keep him on a leash, and not letting him jump up on the couch for a while, just tug him back off with the leash. Keep it blocked off when you are not home might help that. He needs to learn the couch does not belong to him. And as a bulldog, it is probably better for his joint health in the long run not to be jumping on and off of it anyway.

Get everyone in the family on the same page! No dog on couch, ever. And maybe consider some obedience classes just for fun for both of you, and to reinforce the relationship between you and the dog.