Whether your student is a grad student or undergrad has no bearing on whether you can claim him as a dependent or not. A student is a student, whether high school, college or grad school. What matters is age and support. The student must be under 24 on 12/31/19 and must not have provided more than half his own support for the year.
Student loans (grad or undergrad) are counted as "paid by the students own funds" , unless you co-signed the loan.
You can claim the more generous American Opportunity credit , for one more year (split undergrad / grad year), assuming you have claimed less than 4 times before. You may only count the undergrad expenses.
