This is just my opinion, for what it's worth. I have not completed ROTC, but I have participated in a PT/Calisthenics based programs that had similar elements.
Unless I am misunderstanding the lifting program you outline above, you are not actually doing Starting Strength. I believe the basic template for SS is : Day 1 - Squat 3x5, Bench 3x5, Dead 1x5. Day 2 - Squat 3x5, Overhead Press 3x5, Power Clean (or pull up) 5x3. You alternate 1,2,1 one week and 2,1,2 the next. At least, that's how I read the program. I'm not saying that SS is the only program out there, or even the best. I'm just saying that if you're going to do it, you should do it like it's written.
Regarding food, keep an accurate food log and actually plug your calories/macros into a calculator and stay as consistent as possible. Most guys are eating less than they think. Don't worry too much about supplements unless you've got a bunch of extra money, just focus on quality food and lots of it. If you want to try some supps whey protein, BCAA and fish oil are good bets.
Rucking, running and calisthenics are good focuses, as they are "likely" on the agenda at ROTC. You can ruck almost every morning for 30-45min without doing yourself much harm as far as recovery goes and you should probably run 3-4 days a week, mixing shorter distance (400m+-) sprints, hills and one longer, slower steady state run. Do yourself a favor and start building good running form now. You can work calisthenics in throughout the day in multiple, smaller sets. Make sure you keep fed, hydrated and rested to recover from your training volume and grow. Good luck and train hard.