I'm afraid that someone there wasn't quite clear on how FMLA works in terms of their explanation. It doesn't matter if you were on "short term disability" for the other five weeks and this employee rep somehow separating in his/her mind what was FMLA and what wasn't. Any reference to "short term disability" would seem to point to an internal policy or pay continuation program vs. anything to do with the law protecting you from losing your job for 12 weeks.
You need to get the lawsuit thing out of your mind. Ultimately, while someone violated FMLA regs by not clearly laying out what FMLA means, that doesn't mean there was any harm done in terms of them running afoul of the law. FMLA protects you from being fired for being absent from work for 12 weeks, but you got yours, so ... (and it isn't as though you'd have magically been ready to return from work weeks sooner regardless even if they'd told you from the first moment you needed to be out (the 5 weeks) that you only had 12 weeks' worth of job protection).
"The thing thats really shady about it all is that my direct supervisor had called me every 2 weeks to get status on my leave ..."
Well, she oughtn't have unless your medical certification/status was up in the air and you or someone else was wishy-washy about how long you'd be out (if you were, that's presumably why; if the powers that be had info that you'd be out until X date and someone didn't convey that to her, they made a mistake). It doesn't really matter that she sent email to the wrong address -- that's a red herring issue. Doesn't change the fact that you got your 12 weeks' worth of job protection.
They wouldn't need a reason to let you go the moment you'd used up the 12 weeks; if someone there thought otherwise, they were mistaken.
Can't know whether it's possible for you to get the job back, but ultimately, if you did, it wouldn't be because the employer was obligated to do so (even if they'd flat-out fired you only after being gone for 7 weeks total).
I'd file a complaint with the federal DOL about how they mishandled dissemination of info (though of course they could pretend as though they didn't -- don't know how successfully). You're free to see if someone's so ignorant of the regs that they'd cave to a nasty letter from an attorney, I suppose.