U work a 5am to 2pm shift and plan on doing what you've done and use my slow cooker. I bought the Paleo slowcooker cookback. Right now I've been grabbing a rotis' chicken from the store, bag of lettuce mix and a bag of apples. I do all my work meal prep the night before, so all I have to do is throw the ice pack in my lunch bag, toss all the food in, zip it and go.
I've taken sardines a salad and fruti in fro lunch too. I think you're on the right track, keep it simple that covers your needs. I take extra meat and fruit in for my breakfast meal, it pays to have extra so temptation doesn't creep in. I have scavenged meat from sandwiches in the cold food machine and tossed the bun--that's been on days I'm hungry between my two meals.