Wow. This is such a powerful and thought-provoking piece ... I lack anything more coherent than that right now, but I have goosebumps after reading it.

I've always wonderd about what release exactly the Lay is. I thought it was death, nature, fate itself ( which is of course sort of ruined by the fact that everything in Middel Earth is predestined, but..) - what Luthien does is utterly unnatural. She escapes being reborn and living for ever, escapes the world itself. It was always the lay of Luthien to me - she is the escape artist throughout, from Thingol to Morgoth to the very fate of all her people. I never really saw the lay as being about Beren's release too, though now I think I can. And Finrod..I never thought of it as a release for him. But it must have been. He had his father again and maybe even Amarie too, finally. 
"Really?

There’s nothing real about any of this!

Then what is it we are waiting for?

Leithian. The sob of the nightingale. Release from bondage."

Wow. Those final sentence just struck something. Beautiful. The lines about John and Edith and spring coming into blood again, too: such an abstract story suddenly very personal, much more real. Great writing!

I keep coming back to this, whenever I reread Of Beren and Luthien. Your imagery and meditations have stuck with me over the years, and continue to "smote my heart" as much as they did the first time, if not more. Well done!