westinghouse,
a) all of it would be available! Volume-wise, the fwd inner tanks are around 50% of the capacity of the aft inner tanks (that doesn´t mean they contain fuel in that relation in the moment when you split the tanks!). Both sections have two pumps each (main and standby).
b) yes, it would. If I remember correctly, ECAM will not show you the quantities of the fwd and aft inner tank separately; it only shows the "inner tank" quantity.
Hope this helps,
J.V.