Well dang... looks like that 20 inches a year is a problem.
you did make notes: in your report about basements and sub-structure walls can leak ?

I think the only to keep this water out is some type of a drain system. and thats going to cost a few bucks to put in and then the only thing you can do is sit back and over a few season see if it works.

these is just about nothing I can think of the you can do from the interior.

Best

Ron