hope you don't mind, but i too am interested in doing this, and i have begun research on him already, and i think i might know what fabric his coat is made out of.
i was looking at it and it came to me, when if the fabric his coat was made out of similar to that of fabric some weaved carpets are made out of? Or better yet, upholstery fabric
closest i can find on the internet is this, but it is poly urethane coated
the funny thing is i am a cadet in the same garrison you are in so maybe we can work together on it! in the mean time i shall try to get more pictures of kylo rens outfit at CVII.
and as far as where he belongs, he might be moved to the sith lords detachment.
(and sorry if i hijacked your thread a little)