Lauren,
I have been through this with Adobe over chat and over the phone since this thread. They do not have a solution for the problem other than to say it is your problem not their's. If they did have a solution they would have implemented it into the Typekit. I have consulted with other resources and found that Adobe's fundamental flaw is that they are selling something outside of their capability to provide. The Typekit tool is extremely complex and easy to work with but cannot fulfill the requirements for readable text across all platforms. To be fair neither can Google.
The only answer I seem to be able to get from the people at Adobe is that it is the wrong font to use for text. An absurd insinuation on its face since Mac can render it properly. I would imagine that this conversation should also involve some of the programming engineers at Microsoft (whose tech support is much better than Adobe yet still say its "Adobe's failures in programming", their words not mine) in finding a solution to this issue but in the end I showed my client the thread and explained how the font he wanted was not cross browser supported and we simply selected something else that was.
Long story short, the fonts do not function properly in the PC environment at the smaller sizes, Adobe is not able or willing to reprogram them so they do and any attempt to get a straight answer out of them as to why leads you into a circular logic that makes you want to uninstall the entire suite. If there was an alternative...
Sorry to seem so down on Adobe but after 20 years of using them and encountering these issues time and time again the discussion gets old.
Hope this helps you,
Brett