Well today went a lot better. The little 400W battery pack still went from FL (full) to LO as soon as I connected it (which is inexplicable, because it's not measuring the car battery, it's measuring itself), so I called a local tow guy and told him I'm in the parking garage, so he can't bring his truck, and he actually seemed to brighten up at the prospect, and when he showed up, he showed up in a cab with his family, and he pulled out a battery pack that wasn't that much bigger than mine...alright, it "wasn't that much bigger" in the same way that a porn cock "isn't that much bigger" than mine (they are*), but it was rated at 1200 Watts and started her...er...I mean, my car right up. Hey, so now I had a way to warm the battery up and charge it! So I drove around for about an hour (including nervously stopping in the middle, briefly), and I will check on it again in the morning.
*...or so I hear...blah blah blah...that's what she said...