Your world is very well visualized and described. I like how it really seems to be coming at me through Frodo's senses. Also I love the concept of an adventure between Arda and Aman.
That said, I find Eltir's made-up dialect jarring. It doesn't operate by any set of grammatical rules I recognize. I'm all for you inventing a dialect, but I think it would be wise to sit down beforehand and think up the grammatical rules (eg, is "thy" a subject pronoun or a possessive adjective? Is 'tis not short for "it is" ?)