Sorry I can't help with the shoes. When I have slide problems it is almost always sticking caused by me going over to the snack bar without a shoe cover.
With your shoulder problem, are your shoulders level in your stance, ( before starting your approach ) or is your ball side shoulder dropped slightly? In theory you should let the weight of the ball pull the shoulder down so that you don't waste energy fighting the weight of the ball. It has the added benefit of putting your eyes closer to the path of the ball. Hope this helps.
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