Lee,
You said it in the first post, you said you are trying to pull through the clicker while "concentrating" on the target. If you are concentrating on the target, you are not concentrating on pulling. Once you get your sight picture, gap, etc., just continue to watch that picture. It will center itself, if you allow it to. Once the aiming portion of the shot has been completed, switch you concentration to pulling by talking yourself through the shot. More specifically, say to yourself, "Keep Pulling, Keep Pulling....." until the clicker goes off and the shot is released. It is a mere matter of what you are thinking about during your shot. You have no problem with it in your living room because you are thinking about pulling. On the range, you are switching your concentration to the target, which takes directly away from your pulling. Your conscious mind can only do one thing at a time. Give it that one thing (pulling) to concentrate on by saying those words (Keep pulling) to yourself when you want to activate the shot. Your shot will then happen in the speed you want it to. Remember, your muscles will move in the exact rhythm that you say your mantra (keep pulling, keep pulling, keep pulling...). Say it smooth with no breaks between the words. Hope this helps.
Merry Christmas,
Joel Turner
Masters of the Barebow 4