I Wish Someone Could Answer These Questions About thew Problems I See in the Pre Trib Rapture ScwnaEIO

Just heard MacArthur lay out the pre-tribulation rapture scenario and as usual I'm left with the same questions after all of it, qhich lever get answered or even addressed.  I get the logic of the basic scenario and it's very compelling, very persuasive, but nevertheless I have a problem with elements that seem to be left out,k or taken for granted.

How can there be two bodies of believers who have all the characteristics of the Church but only one of the greoups IS the Church and the other is the Tribulation Saints?  While "the Church" is in heaven, having been raptures before the start of the Tribulation period, others are being saved during the tribulation, some martyred, some managing to escape death to the end, all sharing exactly the same characteristics as the Church possesses and yet they are not the CHurch.  All I ever hear from the supporters of this scenario is that, well, that's just the way it is.  Those people are not th Church because the Church has been raptured and is in heaven.  Yet there is nothing about them that makes them different from the Church believers and I see nothing anywhere in scripture that suggests that there are to be these two separate groups of believers atg the end, all believers according to the same standards, all saved by fatih in Christ's death and so on, all the same and yet one group is the Church and the other is something else.  I don't get it and I don't see how nobody else sees this as a problem.

Specifically I have a problem with the different groups of martyrs.  The martyhres under the altar in Revelation Six after the opening of the fifth seal are waiting for another group of martyrs to join them so that they will aoll receive their rewards at the same time.  Presumably these are martyhrs made during the events of Revelation Six since the martyrs that were made during the church Age of the last two millennia have been raptured and are in heaven with the CDhurch.  Yet they are martyrs just likie those under the altar and like those yet expected to be martyred during the tribulation.  If Martyrs are being treated as a group unto themselves, how is it that those with the raptured Church are just blended in with the church and not separated out as are the other two tgroups?  Those in the raptured group would include all those martyred under the Caesars, especially Nero, in the early centuries, and all those mayrtyured under the Rom an Catholid Church of the Middle ages, millionsof them as memorialized in foxes' Book of Martyres.  It makes no sense to me that this group of martyrs would be treated as just part of the raptured church while other martyrs that come during the tribulation ate treated as a separate group, or two separate groups.  

I've said this many times beofre and here it is again.  I continue to see it as a question that needs an answeer, and I continue to susepct that it called the whole pre trib scenario into queisotn.  Not that I have an alternative in mind.