As long as your horse is genetically palomino, you SHOULD be able to register him/her. Sometimes chocolate taffy/silver dapple horses can appear a smutty/chocolate palomino in colour but their parent's colours would distinguish this from a dark palomino. I have a palomino that is an 'ideal' palomino according to the registry, as he is deep, rich gold with a white mane and tail in summer, but the society nearly rejected him in his winter coat as he goes so pale, like a grey, they didn't think he was 'palomino enough' (or words to that effect). His summer coat saved him. But your horse is definately a pally, no matter what colour he sheds to. It would be interesting to see pics of him when he has shed, to see what colour he goes.
The half-halt is also used as a "hey poneh, I am gonna ask you to do something in a second, is yew awake?".