The 744 tail tank is just somewhere to stuff extra fuel. It is not designed to be a trim tank as in the A330/340.
It's one tank, so if one pump fails the fuel will still transfer via the one operating pump. I don't ever recall hearing about a dual pump failure. It's usually the last tank to get filled on a high fuel load, so it only ever gets used on very long flights which reduces the incidences of this happening.
Certainly, the FUEL STAB TFR EICAS message will get your attention. But the C of G implications of such a failure mean you have to land with a minimum of 15.9 tonnnes in the inboard wing tanks and as this message will occur fairly early on in flight, you will have plenty of time to think about it.