I strongly urge you to name your custom template something other than "normal.dotx."
That name will lead to confusion, especially if you have display of filename extensions turned off (the default in new installations). "Mynormal.dotx" would work fine as a substitute.
For more on the Normal template, see my
article on templates.
If you want existing documents to have the characteristics of your own template, the simplest method is to create new documents based on the template and paste the content from the old documents in the new ones, then save.