My friends dad in his late 60's wanted to learn math and used the No Bullshit math and physics from https://minireference.com/ and loved it. Their Linear Algebra is quite good too.
and standalone concept maps that show the prerequisite graph (very useful when learning from any book): https://minireference.com/static/conceptmaps/math_and_physic... and https://minireference.com/static/conceptmaps/linear_algebra_...
I recently released a new book with just high school materials, specifically targeted at adult learners. Check out the website here: https://nobsmath.com/
We can't wait for your stats book to be released.