A (Shadow elves):
3000 BC: Great Rain of Fire, elves driven underground
2200 BC: Other elves settle in Glantri (where shadow elves used to live)
1950 BC: Shadow elves resettle in Glantri, no contact with other group
1700 BC: Glantri cataclysm, shadow elves return underground
1420 BC: Shadow elves find Atzanteotl's temple, drive out Azcans, build 
         Aengmor. Worship of Atzanteotl begins.
1290 BC: Atzanteotl drives elves from Aengmor.
1104 BC: Shadow elves discover the Refuge Of Stone, switch worship to 
         Rafiel, build City Of Stars and take the name of Shadow Elves.
896 BC:  Expedition of Shadow elves reach Hollow World. Few return.
792 BC:  Second shadow elf expedition reaches outer world in the broken 
         lands. Conclude that surface is uninhabitable.

B (Schattenalfen):
3000 BC: Great Rain Of Fire, survivors (shadow elf ancestors ) burrow 
         underground. Subtly guided by Rafiel, they discover the miles 
         high high caverns of the refuge of stone and build City Of 
         Stars. 
1700 BC: Glantri cataclysm, elves from Glantri discover City Of Stars and 
         are welcomed. They adopt the clan name of Schattenalf, which 
         means "Shadow Elf" in their elvish dialect. 
1500 BC: Expedition of Shadow elves reach Hollow World. Few return. 
         Atzanteotl reaches immortality. Atzanteotl begins corrupting 
         schattenalf. The Schattenalf turn from Rafiel to Atzanteotl. Two 
         groups of schattenalf leave the City Of Stars.
1420 BC: First group of schattenalf reach a cavern near the surface of 
         the outer world and build Aengmor.
1400 BC: Second group of schattenalf reach Hollow World and settle there. 
1290 BC: Elves of Aengmor obliterated. 



C (combined):
        3000 BC: Survivors of the elven colony near Blackmoor flee to 
the newly-formed Broken Lands; they burrow deep into the ground 
to survive the aftereffects of the Great Rain of Fire. These 
are the ancestors of the Shadow Elves.
        2200 BC: Some elves break off from Ilsundal's migration 
and eventually find their way to the frozen valleys of Glantri, 
where they settle. A few survivors from the second migration 
from Vulcania also reach Glantri and settle among their 
cousins.
        1950 BC: Shadow elves resettle in surface Glantri, no contact 
with other group.
        1700 BC: The elves of Glantri discover, in the Broken 
Lands, a strange artifact from the lost Blackmoor civilization. 
They tinker with it, and the artifact explodes cataclysmically, 
sending impenetrable clouds into the sky (which last for 
years), and spreading a strange rotting plague among the 
surviving elves - those who were far enough away to survive. 
The elves shelter themselves in the deepest caves of Glantri. 
They find an incredible series of caverns there and begin a 
years-long migration. The traveling tribes are separated from 
one another. These are the ancestors of the Hollow World's 
Gentle Folk, Icevale Elves, and the Schattenalfen. A fourth 
group, led by an elf named Atziann, has no survivors save that 
king. Some emerge, years later, hundreds of miles south, past 
the Broken lands. Some perish. 
        1650 BC: A surviving clan of Glantrian elves from the 
outer world finds its way to the Hollow World through 
thousands of miles of subterranean passages. The tribe emerges 
in lands thickly occupied by hostile Neathar tribes and 
dinosaurs; they migrate northward, to lands similar to frozen 
Glantri, and settle in the mountains south of the Beastmen and 
west of the Antalians. They call their new land Icevale. (HW)
        1500 BC: The elf Atziann attains Immortality and adopts the 
Azcan form of his name, Atzanteotl, "Atziann the Divine." He 
begins whispering to selected Shadow Elves of the power and glory he can 
bring them, and lures them away from their faiths. Increasing numbers of 
Shadow Elves (especially those of the Schattenalfen clan) turn from the 
worship of Rafiel to that of Atzanteotl.
        1420 BC: The underground elven wanderers stumble upon 
Mictlan, and overthrow the humans. Those elves who have been 
seduced by Atzanteotl declare that the temple is sacred to him, 
and he has given them victory over their enemies and a place to 
call home. These elves become the Schattenalfen. Most of the 
elves are uneasy about this alien Immortal, but they are weary, 
and so they settle and build the city of Aengmor. All of 
Atruatzin's followers are slain; he alone escapes.
        1400 BC: A colonizing party of Shadow Elves, mostly Schattenalf 
followers of Atzanteotl are driven out of Aengmor (by the will 
of their patron). Retracing an earlier lost expedition's 
path to the Hollow World, they emerge just north of the great 
equatorial mountain range.
        1395 BC: The Schattenalfen are badly beaten by the 
Kogolor dwarves and must break off the war. They continue 
travelling west, to an area not infested with dwarves, and 
settle there. But due north of their new lands are the Azcans, 
whose culture and architecture are disturbingly and 
insultingly like theirs (a result of Atzanteotl's guidance of 
the Schattenalf culture, though they don't know this); the 
Schattenalfen hate these people, whom they see as a mockery of 
their culture, and begin an ages-long war with the Azcans.
        1290 BC: The outer-world Shadow Elf city of Aengmor is 
"destroyed" (actually, merely surrounded by lava and made 
uninhabitable) during a volcanic eruption; many Schattenalfen 
escape, burrowing deeper into the crust of the earth. Actually, 
this is part of a grand scheme of Atzanteotl, their patron. 
        1104 BC: Underground elves discover the Refuge of Stone 
and take the name of shadow elves unto themselves. Building 
work begins on the City of Stars.
        1000 BC: An expedition of Shadow Elves leaves the City of Stars 
in an effort to find the path to the surface world. Instead, they find 
their way to the Hollow World, where they are fatally poisoned by the 
rays of the eternal sun. Some of them make it back to the City of the 
Stars with news of their voyage, but all soon perish.
        896 BC: First shadow-elf exploration to the surface 
world ends in disaster with few survivors.
        792 BC: Second shadow-elf expedition to the surface lands 
emerges in the Broken Lands. Failure of this expedition leads 
to abandonment of further attempts to reach surface.




 Your neighborhood unofficial Timeline keeper to the rescue... :) Taking 
a look at your points, I see a few blunders by TSR:
 a)

Anyway, here's what I understand to be 'what really happened'. :)

3000 BC: The Great Rain of Fire. The Blackmoor elves (ancestors of the 
         Shadow Elves, Schattenalfen, Icevale elves, Gentle Folk, and 
         Atzanteotl) are driven underground.
2200 BC: Elves (not the Blackmoor ones) settle in Glantri.
1950 BC: The Blackmoor elves settle in surface Glantri, and never 
         contact the other elves.
1700 BC: The Glantri Cataclysm. The Glantri elves are destroyed. The 
         Blackmoor elves once again go underground, splitting up into 
         individual clans.
1650 BC: Some elves reach the Hollow World, and become the Icevale elves 
         and the Gentle folk. Atziann, sole survivor of his clan, also 
         reaches the Hollow World.
1500 BC: Atziann becomes an Immortal, renaming himself Atzanteotl. He 
         begins whispering to various underground-Blackmoor elves 
         (especially the Schattenalfen), luring them away from their 
         faiths.
1420 BC: The Schattenalfen reach the Hollow World, then go back to the 
         outer world and build Aengmor.
1400 BC: Some (but not all) elves are driven from Aengmor, and settle in 
         the Hollow World. These are the modern-day Schattenalfen.
1352 BC: Aengmor is finished being built.
1290 BC: Atzanteotl sinks Aengmor. Many Schattenalfen escape, going 
         underground.
1104 BC: The ex-Aengmor Schattenalfen discover the Refuge of Stone, 
         convert to Rafiel, and become the Shadow Elves.