If I can't claim my sons tuition because he wasn't in school for 5 months can he claim it?

Probably not.

A student, under age 24, is only eligible for the refundable portion of the American Opportunity Credit if he supports himself by working. You cannot be supporting yourself on parental support, 529 plans or student loans & grants. You must have actually paid tuition, not had it paid by scholarships & grants.  It is usually best if the parent claims that credit.  

However, if he has a tax liability and does not qualify as your dependent, he can claim the non-refundable part of the tuition credit. That is, he can get his tax liability reduced, but he cannot get a refund.

Yes, to part 2 of your question. You may claim the tuition paid, even if he dropped out. But for you to claim it, he must qualify as your dependent. If he claims the credit, he may count tuition paid by you.