Python 3, score = ack(126,126)/100^3

g=len('"');i=ord('~');f=lambda m,n:(f(m-g,f(m,n-g))if n else f(m-g,g))if m else n+1
print(f(i,i))

The f function is the ackermann function, which i have just enough space to invoke.

Python 3, score = ack(126,126)/100^3

g=len('"');i=ord('~');f=lambda m,n:(f(m-g,f(m,n-g))if n else f(m-g,g))if m else n+g
print(f(i,i))

The f function is the ackermann function, which i have just enough space to invoke.

Edit: previously "else n+1", which was in violation of challenge rules- kudos to Simply Beautiful Art.