I can answer a few of those:
You should take the ASTB before you finish college. If you're already done with college then thats certainly not an option - in that case take it as soon as you can. But you don't need to wait until you graduate before you can take it (not sure if you meant it that way or not).
Also, after OCS, you will go to API, then the various phases of flight training, and you will need to go to SERE school. When you're done with all the training, you go to a training squadron to train in the aircraft that you will be fliying. So there will be many things between OCS and getting out to the fleet. What you have listed for step 3 may take a few years to complete from start to finish.
You should take things one step at a time. There are no guarantees to what (or if) you will be flying. Hopefully I didnt post anything incorrect here - someone please correct if so. Read around this site to learn about the process and everything it takes along the way. You can learn a lot just by reading all the threads pertaining to training, processes, etc. for a few days/weeks depending how much free time you have.
If you want to study up for the tests, get the ARCO book and read up on a few ASTB threads here. Theres a lot of good info up here. But please read through the ASTB threads before starting another one to ask questions because it might already be covered in another thread. If you get a score that is too low to be a pilot, then you won't get selected for it (but its really the whole package that you put together to apply thats looked at).
Hope some of that helps.
