Krista, if you're husband's military, you might want to talk to his command and see what plans they have in place to help the dependents if needed. Some places might be well-planned, others might be utterly lacking.

Re: knives - guns are typically much more complex. If you can handle a .40 compact, I'm sure the knife will be fine. The big downside of a Mora knife is that it's typically smooth handled, but they make some with a decent finger guard at the pommel. Ragnar's has a good selection (google him, yes, it's spelled correctly).

Food. Definitely second freeze dried, vice MRE's. Or, at least keep FD for the "sit-down" meals, ie, dinner. MRE or similar for lunch is OK. Pick your poison for breakfast - I used to do just instant oatmeal, grits or a power bar when I was camping a lot. Maybe consider a small fishing pole and kit. Fish would be a nice change of pace, and sometimes you can cut back a few pounds if you catch enough to feed yourself. Remember though, if you're bugging out, so is half the state...

Ultralight tents. No real preference or experience. I have a REI 1-person tent that I love. Probably most of the big name stuff will be fine. North Face, REI, Marmot, Outdoor Hardwear. You might want to find a good ultra-light forum and lurk for a few weeks before you purchase some of the bigger items, like tent, water filter, even a pack.

Clothes: Just make sure that you dedicate a lot of good quality, synthetics for you and your kid. I'd consider 3 pairs of underwear for each (kid's potty trained, I hope?) and 6 pairs of socks. You can rinse/dry as you filter water.

Regarding feminine hygiene. Don't know how many you packed, but if you're truly going to go 400 miles, I'd consider packing enough for 2 cycles. Murphy's law says it'll come twice, just to screw with you. On the other hand, biology sometimes will keep Aunt Flo away under an increased exercise burden... things to consider.