I have the exact same experience.. I'm in my 30s and have not done maths since I was 16 and it doesn't help that I have mild dyslexia
Get the Manhattan foundation books
And the other
Manhattan prep books
I wouldn't bother with the advanced quant book
I'm not saying it's bad .. infact it's very good but i have used it and if you have a problem with maths , it probably won't help much because of how advanced it is. Only get it once you get to a good level
At the moment I score between 40 and 47 on practice test but If I paced my self better and didn't panic I could score a lot more because half the time I go back and look at the question and realise how easy it was.
It's not only about the maths though .. strategy has a lot to do with it .. there are loads of short cuts to answer questions and it would help memorizing some general maths principles like the powers of 2 or the diagonal of a cube or square ..