Well the only problem with them being at full strength (this answers the second bit too) is that they'd struggle like all hell and the vampire might have a very hard, if not impossible, time trying to do it without injuring them first. Their will is of little importance, as to the third bit.. I'm not really sure. My guess is since undead in WHFB seem to be magically moving then the magic would indeed allow them to get up straight away. And even if it didn't, Invocation of Nehek. 
