You need to take it to another dealer because they just aren't willing to do anything obviously. It has been cold here in SE Michigan and I haven't had any problems. My Mustang sat all week this week, with temp in the single digits, and last night with a temp of 15 degrees I decided to take it out and it started up with no problem.
If a different dealer can't fix it, then it is time to call Ford customer service rep for the area. The "doesn't like Michigan winters" excuse is unacceptable. I see that you are a student in Mt. Pleasant -- so the local dealer may be figuring you won't be around long and can be given crap like this because it doesn't affect his bottom line. When I lived up there I didn't have any problem with that dealer, but then I wasn't a student.

 

MAKE the dealer fix it!!! Trust me, it has nothing to do with the Michigan winters...I live just north of Columbus Ohio and it has beennearly as cold down here...I only go out and start my car maybe once every 2 weeks...it just sits in the garage (non- heated either) but it fires right up every time. There may be a tsb on this, check it out.

 

i belive i know the problem. ford has something called a "jem" in the car. its part of the factory alaram and many other things in the car, it acully send s a pulse threw ur car when its armed,(thus why when u do an aftermarket alaram it might go off every 45 mins) its programed in the ecu and sometimes with a tune u can accidently turn the jem off, once off it cant be turned back on(unless its put the sleep which is done when an aftermarket alarm is put in) once the jem is off it aculy will drain ur battery if the car is not driven or turned on every 2 days or so, i'm certified as mobile electronics installer and have had a couple fords where the jem shuts off and the car dies every 2 days, i would go to another dealership, even if its a little father drive and tell them to take a look at it, more or likely the dealership u went to dosent want to do the labor involved in turning the jem back on.(if its off you have to replace the whole ecu i belive and reprogram,) thats my 2 cents