I also use a 14 in. round hoop. Get them at Joanns for a couple of bucks. I place the sandwich in the hoop relatively tightly, smooth my top and backing and then loosen the sandwich by pushing the top down a bit around all the rim of the hoop. I will also sometimes work hoopless. Just depends on the project. Your practice piece might just be too small to work comfortably in that frame.
I hate John James needles. Tried many different ones and found that I do best with Roxanne needles. I started out with (don't remember brand - probably clover) #9's and have worked my way to #11's and #12's.
Don't worry about the knot. Just make one that works. I've never been able to do the 'quilters knot'. And amazing, when my mother tried to teach me that knot 50 years ago it wasn't called that. Guess what - a knot is a knot when it comes to embedding it into the sandwich.
I use Thimblelady timble. Dimples on the sides are much deeper and I find it easier to push with the pad of my finger than the tip. Bloodshed will continue to occur until you build up a callous on your bottom finger. It's a trial and a learning process. Don't make yourself crazy. Take your time, relax, and you'll eventually get there.