You read the MRG
1) That depends on the AOA on the stabilizer, it will go in whatever direction the relative airflow pushes it, if for instance you have more nose down trim than necessary in the current flight situation the stabilizer will 'fly up' (leading edge up relative to the aeroplane fuselage)
2) If the stabilizer is actually mechanically loose (like in that nasty MD80 crash) the tiny elevator tab itself is certainly not enough to counter the effect of the massive stabilizer, let alone reverse it - imagine the above case, the stabilizer 'flies away' into a massive nose down trim position (positive pitch relative to the fuselage) you trying to lift the nose with full elevator up (with the tab moving upwards relative to the stabilizer) will not help you in the least, au contraire, the elevator will act like a trim tab and assist the stabilizer in moving to positive pitch...
3) Depends what kind of runaway you are experiencing, if you can rule out an aerodynamic runaway - as far as I know thats in the MRG as well - you can try either autopilot or manual trim, depending on what was in use when the runaway started... Sure, you would need to reset one of the cutout switches for that - and thus act outside the QRH on your own risk
Please correct me if I wrote absolute tosh, just came back from duty, can't be sure I got it together correctly
