unless the document you sign is a national letter of intent, it is non-binding and not worth the paper it's written on. my understanding is the minimum d1 scholarship is now 30% (that is what we were told and were a 2012 sign). apply for all your aid and admission to that school and continue to look for a school. if someone asks you if you have signed the answer is no, and if you get an offer you like take it. i would look hard at a good juco unless you're just dead set on the freshman d1 experience. if the guy really wants you he'll offer you 30%. if not, you owe him nothing. you can always show up the first day since you are a walk on. you can also go through fall ball and transfer at semester if you don't like what you see.