A family of four living on an E-5 salary will not qualify for food stamps. The military has a program for large lower enlisted families that covers the gap that allows them to qualify for food stamps so that the money comes from the military instead of the state.http://usmilitary.about.com/cs/money...foodstamps.htm
You do, of course, qualify for WIC. I couldn't get from your other posts whether or not you get WIC.
It sounds like a pay advance would be a bad idea. If you can't afford to live on what you have now, it doesn't seem like a good idea to reduce that paycheck even more.
It seems that there are other problems, aside from the truck. I'm not judging, Maude knows that I've been in similar tight places for one reason or another, but you and your husband need help figuring this out. I'm not sure what the name of the Army's relief agency is, but in the Air Force we call the Family Support Center and set up an appointment with a counselor and they try to help you figure things out. They can get interest rates lowered, Military Star payments lowered, point you in the direction of other emergency relief agencies, and help you figure out a way to live on what you have. Anything you do right now is going to be a temporary fix, which is necessary, but I disagree that you don't need to think long term because that is the only way to prevent this from happening again.
Please rethink your vehicle needs. When we were in Texas in '04, we only had one car because we were en route to Hawaii from Monterey. It was only four months, but I got every morning and took my husband to the base across town with my 6yo, 2yo, and very tiny baby. It sucked, but I had to do it because I also had to take my 6yo to school. (There was no bus and no sidewalk on the very busy route to the school. It was truly insane.) But we did it. Also, I've gotten all three of my kids in the backseat of a '90 Honda Accord on a regular basis. Until recently, our primary car was a Hyundai Elantra, not exactly roomy. It was tight, but we did it and everyone was just fine. You don't "need" an SUV or even a minivan with three kids, I promise. If the truck is still in good shape, it is possible to just turn it in. We had to do that with my dad's truck when he had a stroke. We couldn't get what he owed on it, so my mom just called the dealership and explained and they took it back. It went on her credit record, but she just needed to get rid of that payment.
Ebay and Craigslist are good ways to make quick cash. Your husband can also deliver pizzas-- I've known more than one soldier that did that in the evenings to make ends meet. It doesn't sound like it would be a good idea for you to work with toxemia, but your husband could also get a little extra work on the weekends in retail. He has to get permission from his command, but it's possible.