^^^
Also, would a 730 in Chem help offset a B I received in chemistry or would I be better off sending just 800 Math II and 750 Bio M?
Did you even look at the school’s web site?
http://admission.stanford.edu/application/freshman/testing.html
The answer is right on there.
No
There are no offsets. The application is viewed holistically.
It makes no difference; they are all great scores. Whether they take the 3rd one into consideration or just the highest 2, is another question. But doing either will not affect your chances one way or the other.