You may not split the two parts of the AOC. In order for him to claim the non refundable part, you would have to forgo claiming him as a dependent. But, he doesn't need the AOC to get his tax to zero. $3120 + 7708 = less than the $12,200 standard deduction, so he will have no income tax liability.
As to the crossed years, you use this numbers on the form. It's not what years they were for; it in what year the expenses were paid by the scholarships, that counts.
