Question #1: If my college student wants to claim himself as a dependent when he files his return can I still claim his as a dependent on my return?
No. If you want to claim your son as a dependent and take an exemption for him on your return then he cannot claim a personal exemption for himself on his IRS tax return. Instead, he will need to check the box on his return indicating that someone else claimed him as a dependent.
Question #2: What should I do if I realize I made a mistake on my tax return that I have already e-filed?