Sounds like small dog syndrome. Little dogs bark and act aggressively because they are so small that they are on constant alert. They are tiny and susceptible to being harmed so they have to do this as a defense mechanism. I have a Papillon that barks at everything. I'm still working on that behavior. As far as the peeing when company pets him, that is fear too. Hovering over a little dog, petting, and cooing and saying "good dog, its okay, etc etc" may seem nice and soothing, but its threatening to something so small. I can't stand it when my guests hover over my little dogs crate and try and soothe her barking by bending over and talking to her. I put her in the crate to feel safe and here they are invading her safe zone! No wonder she goes crazy in there, she's cornered and some big dummy is hovering over her! Every time I try and work on her confidence and try to get her feeling safe and knowing that I'm here to protect her, some idiot comes along and sabotages our progress by thinking that they ar being nice and going to make her like them! It drives me crazy, and my dog is actually better off being out of her crate so that she can get away from people when they irritate her.
All I can tell you is make the dog feel safe, protected and let him know that you are the pack leader and he has nothing to worry about because you are there to protect him. Eventually he'll relax and this behavior should subside, if you can get your guests to leave him alone and not make him feel threatened and thwart your training efforts.