isaac,
It is very competitive. I would encourage you to reach out to a Blue & Gold representative for your area to get more info.
I was an engineering major and baseball player. It was a challenge but manageable.
A midshipman does not incur an obligation to repay the tuition until he/she attends a class in his/her junior year. So, if you were to fall prey to the Ac Board (i.e. fail out), you would simply leave. If you do so after you have started your junior year, you would either owe the tuition or time in the fleet as an enlisted sailor/Marine.