You could look into going to West Point if you are a good student or consider ROTC while in college. It is not simply do I want to be an officer or enlisted though kid. Being an officer means you are a leader of soldiers. It is not something just anyone can do and not something you should decide...
You are in a great position seeing as you still have a year. You should be a total PT stud scoring a 300 with another 12 months to work on those. With your running I would turn one of those days into interval training, this will help with your speed. Check out tabata sprints they are killer and...
Going to OCS does not guarantee him the schools he wants. IF he gets Infantry he should get a shot at Ranger, but he is not guaranteed to serve in the airborne or SOF. If that is what you really want than you should enlist as an E-4 with your degree and get it in your contract. Only consider OCS...
Go to google and type in military pay chart. It is very clear what you get paid based on your time in service and rank. Note this is only your base pay though you will get other money from things like BAH but that varies some.