where did enoch and elijah go?
They died. It says in Heb 11:13) These all died in faith, not having received the promises.
Enoch was translated (moved by God) so he would not see death (be killed). Elijah was taken into heaven (the air) to punctuate the transfer of power to Elisha. Elijah eventually died. All men die.
Heb 9:27 And as it is appointed unto men once to die,
who was standing on the Mt of Transfiguration with Jesus?
It was a vision, as it plainly says in Mat 17:9.
in your fantasy scenario where everything happens in the millennium, how does Rev 20 fit your version of the first resurrection (which it states clearly those people have attained)?
Where it is "clearly stated" that enoch, elijah, and moses have attained the first resurrection? The first resurrection is still future.
and in your scenario, then, with all the bad guys in their graves for 1,000 years, WHO IS ALIVE AND PROCREATING DURING THE MILLENNIUM?
People who made it through the trib, people raised in the first resurrection, and us, will be alive. The folks who made it through the trib will be procreating.
alongside disembodied souls (no second resurrection yet) and a glorified Christ?
Not sure what you mean.
and since Rev says all who take the mark go in the lake of fire, why would they bungle through 1,000 years with it just to go into the lake?
They won't. They will be killed in Armageddon and later raised and judged at the great white throne judgement..
In the millennial kingdom will be Christians, those raised at the first resurrection, and those who made it through the trib. And Christ reigning as king, of course. Christians and those raised at the first resurrection will have their spiritual bodies, and everlasting life, those who made it through the trib will still have soul-based bodies. They'll be the one's procreating, and dying (albeit at a much older age). Isaiah 65:17ff.