When working locally with files that contain includes, I use a local testing server so I can check my work. I use WAMP server. The other popular ones are XAMPP and MAMP for mac. So I was trying to ascertain if your local server was working correctly and not contributing to delays in DW. But since you're not using one, it's not an issue.
I don't see anything in your code that leaves me any clues. I do notice my Bootstrap projects are much slower than my non-bootstrap ones but I'm still able to work with them in DW.
Are all your site files on the primary HD with DW and not on a network or 2ndary drive?
Nancy O.