Getting a hang of Microsoft Word styles can be difficult. Here are a couple of issues solved.
Font of a Style overriding main document style
The font used in a word for a style is actually located under Font, and it DOESN’T have to be the name of a font. It can be +Body or +Heading if you wish, to use the default body or heading fonts. Simply choose one of the top two items in the dropdown list (defaults Cambria (Headings), Calibri (Body)) to use the default fonts for the document. Alternatively if you go into the drop down in the lower left corner and select Format / Font.., you can choose either +Body or +Headings to use the Body and Headings default fonts respectively:
To change the DOCUMENT’s default fonts, you have to go to the Design tab in the Ribbon, and select the Fonts dropdown to the right of the Themes listing.