Looking great so far and I love the ideas you've got. <3
If that canal continues to give you grief, I do have an idea. Sandy from Around the Sims has a canal in her Sandy Valley but it's split over three long lots. She wrote a tutorial
here using items from her canal lock set, which is
here. There's also pictures of the canal
here. Finally,
this page has further photos, one of which shows a footbridge over the canal. It might not be what you're looking for but it's the only thing I can think of right now that could help. :)