The history of the Elves is complicated enough from what we do know and what we don't know is probably much greater. I agree that if Lenwe had survived the 1st Age he would cropped up in the hisory of the 2nd Age. Which begs three questions which we cannot answer. 1) How did he die? Well we know Elves do not die of sickness, so that leaves accident or he was killed. If killed who by:Elves, Men,Dwarves creatures of Melkor or wild beasts? 2) Where did he die? Was it in Rhovanion, Gondor, Mordor perhaps or was he the leader of the Elves that made it into Eriador: after all passing down the Anduin the Nandor would have come to Calenardhon and could have by passed the Misty Mountains by the Gap of Rohan.3) When did he die, before or after the return of the Noldor to Middle Earth? Which begs the question what was the role of Denethor. When was he born, before the turning aside of the Nandor or after? If before did he always disagree with his father's actions and thus chose to cross into Beleriand when he could, probably after his father's death? Even if he did, not all the Nandor went with him. So what happened to the Nandor? Well those that chose not to cross the Blue Mountains would have been spread across the lands of Rhovanion and Eriador. Unfortunately we know little of the peoples of these areas whether Elves or Men. It is likely that the wars of the 2nd Age would have driven those that remained into Greenwood the Great ruled from Amon Lanc with a sattelite realm in what would become Lothlorien. The Elves of the White mountains would have dwindled slowly not becoming extinct until the haven at Edhellond caeaed to be used. Which raises another point. We know that some of the Sindar sailed to Valinor from Edhellond, could some the Nandor or even Avari have done so. As for the nature of Silvan Elves these could well have included some of the Avari. They may not have wanted to risk the journey to Valinor, but there is no reason to think that they did not spread away Cuvienen and some must have come west until they reached Greenwood. Unfortnately there are too many questions and too few answers

The history of the Elves is complicated enough from what we do know, and what we don't know is probably much greater. I agree that if Lenwe had survived the 1st Age he would cropped up in the history of the 2nd Age. 

Which begs three questions which we cannot answer.

1. How did he die? Well we know Elves do not die of sickness, so that leaves accident or he was killed. If killed, who by:Elves, Men,Dwarves creatures of Melkor or wild beasts?
2. Where did he die? Was it in Rhovanion, Gondor, Mordor perhaps or was he the leader of the Elves that made it into Eriador: after all passing down the Anduin the Nandor would have come to Calenardhon and could have by passed the Misty Mountains by the Gap of Rohan.
3. When did he die? Before or after the return of the Noldor to Middle Earth? Which begs the question what was the role of Denethor. When was he born, before the turning aside of the Nandor or after? If before, did he always disagree with his father's actions and thus chose to cross into Beleriand when he could, probably after his father's death? Even if he did, not all the Nandor went with him.

So what happened to the Nandor? 

Well, those that chose not to cross the Blue Mountains would have been spread across the lands of Rhovanion and Eriador. Unfortunately we know little of the peoples of these areas whether Elves or Men. It is likely that the wars of the 2nd Age would have driven those that remained into Greenwood the Great ruled from Amon Lanc with a satellite realm in what would become Lothlorien. 

The Elves of the White mountains would have dwindled slowly not becoming extinct until the haven at Edhellond ceased to be used. Which raises another point. We know that some of the Sindar sailed to Valinor from Edhellond, could some the Nandor or even Avari have done so. 

As for the nature of Silvan Elves, these could well have included some of the Avari. They may not have wanted to risk the journey to Valinor, but there is no reason to think that they did not spread away Cuvienen and some must have come west until they reached Greenwood.

Unfortunately there are too many questions and too few answers.