Canvas offers Heading styles, but I also need consistent styles for text.
Probably the easiest (ignoring the politics of the request) way to do this is to get your Canvas Admin to add some custom CSS to your site where you define the styles you need as classes. Then you can use those classes by adding them to the HTML.
The changes made to the CSS are applied at an account or subaccount level, so while it would be possible to restyle the paragraph tag, you would want to do so with care. That's why I suggested classes -- it's more work for you, but it allows the styles to be applied selectively rather than one teacher's desires overriding those of everyone else.
If you need to use a different font, you may need to look at the @font-face declaration of CSS.
Definitely go with the approach James mentioned. You might consider researching web fonts, which would require some css.
CSS Font Stack: Web Fonts
CSS Web Safe Fonts
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