FAA Advisory Circular No. AC 25-13 states (among other limitations) that takeoffs utilizing reduced takeoff thrust settings: Are not authorized when the antiskid system, if installed, is inoperative.
I think question 1 is a stupid question because the answer depends on the engine control system and auto-throttle, if installed. Older hydro-mechanical engine control systems usually maintained a constant RPM (N2) and then EPR would decrease with increasing airspeed (Mach). FADEC-controlled engines maintain whatever they have been programmed to maintain.
Regards,
HN39