You are not helping him at all. It's like telling a 1200 player to study Najdorf theory up to move 30. There is a long way before he can study calculus
I've been tutoring math and chemistry for years. I've had many young students that had little trouble with these subjects -- they just needed a little help developing improving their study habits. LOL, introductory calculus is much easier than the learning the Najdorf.
Perhaps you had an unpleasant experience with math in school, and are now projecting your frustration onto others?

Yes, my dad's a smart guy. I'm reviewing geometry with help from him.
Good, keep it up!
My son got his degrees (BS and MS) in engineering and started at nearly $100,000 per year, right out of college.
Which is good, congratulations! but is your son happy?