Well...first off. <span class="sgc-7"> won't do anything because sgc-7 is only defined for h2 according to your css.
When I find useless spans surrounding every paragraph - and it happens more often than you would think - I just use a search and replace to delete them. in this case I would use:
search: <p><span class="sgc-7">(.*?)</span></p>
replace: <p>\1</p>
use regex and apply it to all html files
That will get rid of the span issue, but it doesn't address the error you said you were having about it automatically adding all that stuff in there in the first place.
As ducks mentioned, you are using inline styles. Personally I would prefer putting all the stuff you have between <style> </style> into a css file and then linking your document to that css file.
I also would clean all the extra sgc-# items off of the css styles...they aren't really necessary - or clean - but you would need to use F/R to clean the document before you delete them. Again, ducks mentioned that they probably come from you editing in the book view. I would recommend minimizing the amount of editing you do in book view...code view is much better and you can see exactly what is going on as you work.