Your body's efforts to heal this have probably stuck everything together like spagehtti that no one bothered to stir. Torn or partially torn PF tendon sounds about right. Muscles have 40x the blood supply of a tendon. They take a LONG time to heal, especially when you're already in your 40s (I am, and I KNOW) and it's a grade 2 or more (which is likely). In the meantime, break up the adhesions by seeing a really well trained massage therapist who does deep, very precise, muscle specific work. If they can't tell you about ankle structure in ridiculous DETAIL, you need to find someone else. Then you need to do stretching with MET, to re-lengthen the calf muscles. If you don't know how, and your therapist can't teach you (or doesn't know) go to my website,
http://www.kaywarren.org, fill out the contacts page, and ask for "MET for the Calf" I'll e-mail it to you.
I won't promise you can do your marathon, but your chances will significantly improve if you get this done.
Kaelyn