Tugboats can be pushers, pullers, or both. Some have squared off bows, some have blunted bows, some have pointed bows. Just do a Google image search for tugboats and you'll see a lot of differe varieties.
The funnel...I don't see a problem with it at all. I'm not sure what problem you have with it, really? You exhaust the diesel fumes up and away because tugs are just as likely to go backwards in their work as they are forwards. So exhausting out the back would end up with a deck full of diesel exhaust and generally unhappy crew. Again, on a Google image search you'll see a LOT of tugboats have funnels to exhaust up instead of out the back.
The tug in the Vistula books is probably a puller, even though it could just as likely push with the stern as well as the bow with proper placement of tires/bumpers.
Room/bunks....tugs aren't meant for a lot of people. Small crew. Slap more people than the usual crew of the tug and you have people sleeping on deck or wherever they can find a spot. They don't make tugs for comfort, they make them for utility and power.
I did a little reading up on tugs, and some of them have the equivalent of a railroad train engine in them. That means power! Pushing a barge (or pulling) isn't going to be all that when those things are used to pushing whole ships like freighters and warships.
Here's a link to a tug similar that in the Vistula module. It's not made of metal.
tugboat picture
If you really want to use a paddleboat steamer, yes, you could say one was salvaged and restored. Though I think it would just be easier to go with the tearing out of the diesel engine and installing a steam engine in its place.
Anyway, I hope this helps some.