I managed to find an answer to my first question:
The Adobe Typekit service provides secure, subscription-based web font hosting for web designers and developers, made possible by the @font-face rule. Typekit subscribers have access to a collection of fonts that can be used on basically any web site. You can view the Adobe Web Fonts available on the Typekit service on Adobe’s foundry page.
Although Typekit relies on the @font-face rule to work, it is different from web fonts used by end users. Fonts remain protected on the Typekit servers and are dynamically delivered to browsers in the appropriate format to ensure an optimal and consistent typographic experience. Typekit offers user-friendly integration with CSS and HTML code, and other optimizations, like font subsetting.
So, @font-face it is.
I've asked another individual with an Adobe InDesign subscription to log into her account and see if she sees the "Unlock more fonts" message when she visits https://typekit.com/fonts/myriad-pro .
Perhaps someone here will beat me to the punch, but I'll update the thread with whatever I discover shortly.
Looks like we're all set!
My colleague is able to access all of the fonts when she logs into Typekit with her Adobe account, so it was simply a matter of having an Adobe ID that is associated with at least one non-Acrobat Creative Cloud standalone product subscription.