Word files almost never copy/paste to an html editor cleanly.
When pasting in DW, right click and choose Paste Special > Text Only (or possibly Text with Structure) to avoid most of the MS-generated gibberish.
Since you answer a lot more questions here than I do, you might want to research the Save as "Filtered" option in Word, which will clean up the markup before you copy it. It works great. After saving a filtered copy of the file, you do your copy and paste task.