Hi @JeffPlatt ...
Just thought I'd chime in here, too. I was also curious as to why you were using Dreamweaver, but your explanation has helped. I, too, used to use Dreamweaver quite a bit when the College I used to work for was using a LMS called Jones e-Education (based out of Denver, CO). When I first started at that College, we were using Microsoft FrontPage, but then I slowly helped transition our course pages to Dreamweaver. Good times...good memories...especially the CSS stuff.
You had mentioned something about exporting your content. Like Doug had suggested, I also typically advocate for people to build all their content in the RCE (Rich Content Editor) of Canvas. But, I also recognize that there are some HTML elements that Canvas strips out upon saving a content page. See Canvas HTML Editor Allowlist for more details on that. I'm not sure if you're aware of this or not, but if you export a Canvas course, it will produce a *.zip file for you. Within the *.zip file, you should find a folder of HTML pages from your course. So, you'd have that as a sort of "back-up" if you needed it.
Do you know if your school has purchased DesignPLUS from Cidi Labs? You might need to have a conversation with your school's Canvas administrator or someone from their Online Learning / eLearning / Distance Education team to see if you have access to it or not. I was thinking that if you had that available, you could build yourself some template pages in your course just the way you wanted them to look. You could use elements that are available within the DesignPLUS sidebar like text boxes, applying image effects, etc. There's a lot more to DesignPLUS than that, though.
Anyway, just thought I'd throw some options out there for you to consider. My $0.02 for what it's worth.
Take care...be well.