Beren and Finrod's half-delirious conversation right before Finrod is murdered is my canon loophole for elves getting sick and the recreation of the Mako posioning I'm using as inspiration. Fan will spend most of his time in Mandos and the Gardens of Lorien recovering his memories, don't worry (the game version is so nice and probably close to how it happens here). 

As fun as this series is to write (and I've having a ball), the yanking on heart-strings wouldn't be as fun without the implicit understanding that they are going to be healed and restored from Mandos before the end of the First Age and that their goal of ensuring Beren and Luthien have a life together and silmaril stolen from Morgoth is fulfilled.