Hi. Don't worry about your chapter length: everyone's writing style is different.
I am not a horse person, but I think you should talk to someone who is, or read up on horses -- maybe beginning with an encyclopedia article or an introductory book for children (both are painless ways to learn basic info about a new topic).
Horses and ponies are different animals: same basic shape, but different sizes (and almost certainly other differences I'm not aware of). So a young horse would not be called a pony (there are various terms for young horses, but I'm not going to expose my ignorance by citing a word which refers to a young horse at the wrong age -- and I think the animal's gender matters too!).
Children who learn to ride at an early age are usually started on ponies because the animal's size is a better fit for such a small child (just as hobbits ride ponies because horses are too large for them). And neither ponies nor horses are all the same size: there are larger and smaller ones, just as there are taller and shorter humans.
Also, this would *not* be Glorfindel's horse Asfaloth, because horses only live to about age 30, and usually aren't ridden for the last few years of their lives. Remember that it is still more than 80 years from the time of your story until FotR: so this horse's name probably shouldn't be Asfaloth, unless Glorfindel makes a point of repeating names (or whomever names horses at Rivendell).
Can't help you with the Sindarin, but there'll be someone else who can. Good luck.
Author's reply
Long review. About that constant change between horse and pony, I used the wrong document. I had fixed that once before. I'll make sure that I fix the horse/pony changes after I type this. After I wrote the story I realized that Asfolath would not be the same horse. Unfortunately, I'm not very a creative person when it comes to horse names, because I am also not a horse person. Is there anything you recommend? If not then Glorfindel names his horses the same thing. *wink* My friend is one of those "horse-people" and she supported your "ride ponies when younger... horses when older" comment. I am either going to say that Estel is an over-achiever or change Asfolath and Glorroh into a pony. Do you know what a pony might be used for in Imladris? Supplies maybe? Thanks for all your help. Thanks for reviewiing.