I just had to skim this thread but something jumped out at me when i read what you wrote above. It's kind of hard to explain but i'll try to give it a shot. The reason those dogs at trials hang out and wait and behave is because they've been taught that they don't get to decide what they will do and when. You say your dog will "bam" to your side on a here command, but he can't walk properly on a leash near sheep. So teach him! And i don't mean teach him a heel command, i mean give him a loose leash and if he tightens it, he gets a leash pop. If he's hanging out with you and starts off towards sheep (or whatever) on his own without being told, notice it immediately and tell him to get his butt back to you where it belongs until he's released to work. Don't nag and beg him to do things right with commands. Watch him and tell him when he's wrong and try to do it as soon as he's made that choice to be wrong.
It's on *him* to choose to do it right, not on you to command him into acting like he's got a brain. Give the dog freedom to do it right, watch his choices and let him know when he's wrong. There is a vast difference between that and commanding a dog into behaving himself. It puts it on the dog's shoulders to act right rather than you trying to *make* him right. Sorry this has to be brief and i hope it makes sense, but you need to do a 360 on how you're training this dog because you're working against each other instead of together. And it sounds like he's winning.