Hi Josh,
I actually had to install the font styles (see attached) provided my a Milsoft rep into Windows font in order to see them correctly before publishing.
I have experimented with creating a layout, adding a legend, converting the legend elements to graphics, ungrouping the graphics, and isolating the symbols. But...how to crop the symbols, make sure they maintain their white color inside and not go transparent, how to get those into AGO, what size should they be, etc...leads to more questions on my side.