Our child suffers from severe anxiety and has been treated by professionals for several years. Some of your posting reminds me of behaviours which describe anxiety; however, the overall "picture" of your stepson appears not to be that of severe anxiety. I also wonder if your stepson might be on the autistic spectrum - whether Asperger's or PDD-NOS or a lesser version, don't know. I do believe Gina04 is correct in that having your stepson evaluated by a developmental specialist might be a prudent decision. I really believe there is far more going on here than "anxiety" behaviours. Perhaps autism, perhaps not .....
Has he been evaluated by a developmental specialist at all? Aside from the urinating issues, he sounds very much like my four year old who has Asperger's Syndrome. One of the symptoms of Asperger's is that they don't really have common sense. Is he urinating in these places because he is angry, wanting to upset people, etc. or do you know? It could be that he needs to go to the bathroom and that for some reason it makes more sense to him to just go in these places. Do a search for Asperger's Syndrome symptoms and see if they describe him at all. Whether they do or not, I would recommend having him seen by a developmental specialist. It was just helpful for me to have an idea of what might be going on with my son and then ask the specialist specifically about the possibility of those things.