I am like this as well for the most part. I’m going to need a lot of paper in order to do complex math (and I was a math minor in college), none of it in my head except the derivative of ex.
That said, on rare occasions – twice in my half a century life – my brain has instantly popped out the answer to a math puzzle and I was correct. But do I know how I arrived at that answer? Nope. My brain told me and that’s all there is that I’m consciously aware of. One of those instances was the winning point for my team in a Math Olympics type competition.
Housework and playing (so long as it involves bodily movement) with children count as exercise. It’s just not Gym!Bro approved exercise but it absolutely is exercise.
And every time you lift your child, consider it a medicine ball or kettlebell lift. Because those devices are actually used to approximate the reality motions you are going through.
What you used to be is lean. You are still fit.