1) Multiply 70,000 barrels times 90 days times 42 gallons per barrel divided by 7.5 gallons per cubic foot.
2) Multiply 400 feet by 400 feet by 400 feet to get the cubic feet.
3) Compare total in 1 above to total in 2 above.
Just going with part of your equation 700000*90 comes out to 630,000 barrels of oil in the Gulf.
Thats a lot of oil in the Gulf and we can all see the effects on the surface and most of it is not coming to the surface. Plus this well has a high content of Benzene and other highly toxic compounds in it
Now I dont know if this could end up being an apocalyptic event or not. I cant see the future but thats a lot of oil and methane plus the dispersants which creates a toxic mix and clearly the Gulf is being damaged greatly.
Go over to the OilDrum where the heavy hitters are. I guarantee you they take this one very seriously and no one over there dismisses the possibility this entire thing could blow out and collapse.