Does it get anyone else that the topic at hand is a crazy acting dog named Marley?
My dog used to be the exact same way whenever she heard fireworks. Every last behavior you described and then some--it was AWFUL! The noise terrified her (and with good reason). I'm all for the med option (not for everyday, but for long trips like you said). Medication was the only thing that worked for my dog, so I completely understand. Sometimes, you just have to go there. However, until you and the vet figure out what dosage is right for your dog (and even after), I second tying her leash to something or getting a doggie seatbelt. If anything's worse than a freaked out dog, it's a freaked out dog who's half sedated. If she's belted down, she'll be less likely to hurt herself or accidentally slam into you while you're driving.