I know exactly how you feel, and I know this isn't what you want to hear but you need to pull through and get it over with. Are you going to get your acceptance rescinded if you get a few B's? No. But you cannot (and I mean CANNOT) throw away 3+ years of hard work because of laziness.
You said yourself that the classes are not especially difficult. At least your parents want to help. I'm a senior too and my parents didn't go to college and have helped me with exactly 0 things since I started college apps. Your SAT is 20pts higher than mine and I'm in the same class rank. You're going to get into Duke as long as you stop being lazy! Colleges will see your senior grades and think you're someone who does the bare minimum in everything.
I probably sound like your parents now, but I know how debilitating senioritis can be. Misery loves company, and I'm sure every senior in America feels how you feel now. Try not to stress out so much; the anxiety will hurt you even more. Try reading a book or do whatever calms you for an hour or so after you come home from school, and then get to studying. I know it sounds impossible, but you will love yourself for it when you get that acceptance letter
Good luck and stay strong!