By no means am I fountain of knowledge in this area but it has been my dream since I was about 16ish to be a college head coach. It is VERY difficult to break into college ranks period.
Honestly, I believe you are doing it the right way by trying to latch on as soon as you graduate. I wish I had done that because now I have 10 years of high school teaching under my belt and 10 years of having a set salaray coming in. As an assistant you won't get paid jack squat and that is what makes it difficult for me. I have had two offers to be an assistant coach but one was for $3000 and the other was for $5000 AND THAT WAS IT. I couldn't do it so I had to turn them down.
Be willing to work like crazy and do everything you can to make it because it's a tough world. If a job comes open there are going to be around 40 some applicants of guys who are already coaching college. So guys like you and I who have no experience have a tougher time making it.
Most head coaches want a pitching coach with recruiting experience. If you can do both it helps out so much in having a chance to get the job. Be willing to work in admissions, finacial aid, dorm director - whatever you can do to make it work.
The two best places to find jobs are
www.naia.org and click on the careers button on the right and another window will popup and you can click on head / assistant coaching positions to browse. They have all sports here so you have to scroll through them to find baseball.
Another place to find them is
www.ncaa.org but this one has just changed recently. You have to register in order to be able to search through job openings. I would give you the steps to do it but I can't remember them but it is very easy to work your way through.
Another source for jobs is the job search websites like monster.cocm and such. You won't find the best jobs here but there are some.
Now as to your question about masters degree I cannot remember a posting (I have probably filled out 200 some applications in the past 3 years) that they did not require a masters degree. But they also want college coaching experience and playing experience as well. Look at it this way - how could it hurt you to have the masters degree? Granted most posts want someone who has a masters degree in PE fields anyone will actually do.
I wish you the best of luck becasue I know how hard it is to break in. You probably already know the stuff I just said but I figured it couldn't hurt to let you know anyway. One last thing - be willing to move because if you wait for one area to open up then your chances of getting one become even more remote.
Good luck again and hope to one day coach with, for or against you at the college level.