re: if top kill fails-keep pumping sea water

So I thought about this some more and I was all messed up originally. First I was using the column of kill mud as part of my hydrostatic calculations but because there is no annulus full of kill mud to surface that is inaccurate. The hydrostatic head that would be generated would be the mud that actually went down the annulus at the wellhead however many feet before the gas forced it up.

Because a 14.0 ppg MW was needed that puts the formation pressures at ~13,000 psi. Since the annulus has been vacated of drilling mud they would have to pump kill mud down ~10,000 feet below the mud line to overcome the formation pressures. That's using a hematite mud at 25 ppg.
There's no way they would get drilling mud that far down just pumping from the top.