No need to be intimidated, your work is great. You can see the love and craftsmanship put into it. That will be with him for many years. Thanks for sharing.
One source that sometimes is over looked is the Stecksstore, it's worth a look. I have not purchased leather there , but I have hardware and it was good quality and fast shipping.
Yes you definitely want to line the clamp area with scrap pieces of leather ( flesh side to the wood). I would not attach needles to the horse, I have never seen it done , just something to get in the way,IMO.
I also belong to the "59" club. I started in the 7th grade , but life fills time, and only in the last 6-7 years have I really gotten serious in the craft. I think as we age that appreciation factor greatly increases. I believe you are at a perfect time in your life to do well .