One of the shifts that happens when a baby moves from baby to toddler is that parenting becomes less about preventing crying and more about helping a child through those very intense emotions that she has. She's not quite there, but she's getting there.
DD is 12.5 months and just recently started getting very frustrated with certain things. Weird things. She was screaming like she had really hurt herself in her playroom...I ran in and found her sitting by her car seat, chewing on the strap. She was furious and frustrated that it wouldn't come loose from the seat!: (BTW, it's the 2nd carseat, still inside from our trip to Florida. Britax Boulevard was great for the plane)
I also agree with finding some time for you....even the 5 minutes in the car thing. You have to do what works. It sounds like this can't continue much longer for you.
Is she eating enough through the day and nursing just for comfort at night? Would a paci work, just for sleep? Do you have a security/transitional object? I'm sure you've already tried these, but they helped us immensely.