There's always a Captain on a boat, no matter the size of crew or boat, the Captain is there as a figure of leadership and order so things don't get out of hand. As for the size of the boat Ulfgar and crew use, it's like the ones docked in Riften, not a big row boat, so it has a sail/mast. It would be a pain, and have to have more crew members than either of us want, if it wasn't a sail, because that would mean rowing, and rowing requires more man power for doing things like going against the river. As for the lookout, he could just crawl up to the top of the mast and sit looking for anything. I'll lower the crew to five because the jobs I stated would be important for a trading ship, and some require more than just one set of eyes or person. Also, the matter of how much can be loaded wouldn't be too much in the first place, considering rivers aren't that deep, and anything more, I could just say some of the crew was left behind to make room and space. Or the shipment could be split between land and water if it was too big.
Plus, if I wanted to, a crew member or two could be killed off while on a job, (like I said, a trading boat could hold all sorts of things to someone interested enough to find out with a sword or bow,) and so mercenaries or others could be hired from Valton that way, or whatever.
And the whole class thing isn't as big of a deal, as you think. Being a mercenary is one of the jobs Ulfgar has history with, and still does on occasion, which is why I put it up. A Blacksmith could be a mercenary, sure, but it's a matter of history. Ulfgar has the history, and continues to do that line of work when need be. Think of it like this, if Ulfgar's trading business went down, or he was in a tavern and someone came in asking for swords to go on some job, he could fall back to the sword and sell his skills that way. It can seem like a mess, but it can also seem like a bit of added detail to exactly the professions Ulfgar is capable of without failure (or too much, anyway.)
What I meant by "No captain is needed" was that there's no need for a captian who works only as the captain. Putting him to do something else means the crew-size can be smaller. The boat seen outside riften is actually bigger than I was thinking about when a river-boat is being talked about.. Is there a specific reason why it must be so big and contain so many crew-members?
Edit#2: If you really, really want the crew to be that big, then I'll add your char-sheet to the accepted char-sheets.
Edit: Daroska, we'll assume the fence Jormaw is sitting on is located in a way that the smith couldn't spot him as he made his way to the farm, mmkay?