Looking at the SketchUp model, I see those duplicated styles, too. I think you can be confident that your cross reference organizer application is the culprit. If you simply purge unused styles, you'll get rid of a few duplicates. You would need to go through and manually do the rest but it won't be that difficult. Find a scene that uses the duplicate, select the original version of the style and update the scene. When you get all finished, purge unused styles again and you should be down to five styles in this model.
I would suggest that for the following scenes, you set the style to Hidden Line with white back and then reselect those scenes for the viewports on the last two pages. Don't let viewports show the scenes as modified. SEC SHORT 2, SEC LONG 5, SEC SHORT 4, and SEC LONG 4.
As for the file bloat, you're right. The use of duplicated styles doesn't help but in addition to some unused styles, I purged what you see below.
Screenshot - 9_17_2018 , 7_08_41 AM.png
Keep in mind that components and materials you may have had in the model space but deleted or replaced remain as part of the SketchUp file. Styles you might use but replace will also remain. Since it sounds like you are combining multiple SketchUp models into one, I would recommend purging unused stuff from the files before amalgamation. Purge Unused from Model Info>Statistics is a good single step method. I use TIG's Purge All because I like to see that little report window to have some idea of what was purged. It's also undoable. I have a keyboard shortcut established for it and run it before closing a file.
