Almost none of this is correct. Elves are immortal, but they are beings of Middle Earth, the First Born. There's a reason it is a big deal that some of them went across the sea after Awakening and saw the Light of the Trees.no you are wrong. The elves are all just one step below the Mair. Heaven is on the other side of the undying lands and the elves live in the undying lands and what we call middle earth is where all the mortals who will die go. Elves are outer planar beings. When they die they reform in the undying lands. As the silmarillion and all the other books are a bit all over the place it gets confusing but that part is not. The reason the elves had to leave in the third age is they aren't mortals and it's not thier realm. After the elves all left the undying lands and heaven were completely seperated from middle earth that's the reason the ones who stayed became mortal. They lost thier link to the undying lands and thier only path was on to the afterlife mortals went too and the elves didn't get to go there they had no idea what it was like. The creations story, the first age and the second age are all part of the creation of the world. It's not done till middle earth is handed over to the Humans. Then all that celestial magic, or infernal magic from morkoth fades away and it become a boring old non magic world.
You should probably reread your Silmarillion before asserting such things.