Watching a dog perform his obedience routine with no lead attached to his collar is a thing of beauty! It appears to be magic, the way he anticipates his owner's moves and wants to just BE there, exactly on the money. Here is how to achieve that doggy ballet of movements.
One secret to good obedience training is never to give your dog the chance to disobey. Make sure he understands the command and what you want him to do, and move toward it with baby steps so he always ALWAYS succeeds. Your happy praise at every turn is what he lives for.
When he is at that comfortable stage on lead where he yawns at every new command, this means he is sure of it and relaxed, then it's time to move on to removing his lead. This will cause a little anxiety at first because his lead is his life line and guide to pleasing you. So make sure everything you are about to show him off-lead is something he knows VERY well with the lead attached.
On-lead heeling, turning and stopping is very smooth and controlled. Before starting off, instead of hooking the lead into the ring, slip the entire lead through his collar, not in the ring, and wrap the end around your hand so you can eat it up as you walk, until the lead slides completely out of the dog's collar. He will barely notice this, just keep walking with no change in gait or tone of your voice, act like nothing new is happening. When you come to a stop and your dog sits predictably at your side like always, pause a moment then PRAISE PRAISE PRAISE! Your dog will look at you funny, as if to say, "What's the big deal? We do this all the time". It's quite funny. That's when you know it has worked the way it should and your dog has made the transition effortlessly.
As you work, keep the dog close at hand, you do not want him to get the idea he can run off. If he makes the slightest off move, take his collar by the live ring and tug. Remember those little tugs that he dislikes so much he learned quickly how to stay in the exact right spot? Remind him that off-lead has the same controls, so you must be vigilant. If he backslides, go back to on-lead. He will learn quickly that he prefers the independence of off-lead work and to get it he must obey your every command.
As to the long line "Come" command, go back to the short line and leave it on the ground so you can grab it if he does not come to you in a timely fashion. Give him no room to think about disobeying. Gradually extend the distance until he is coming to you at a run totally off-lead. He loves this! With patience and vigilance, your dog will be just as dependable off-lead as he became on-lead. And you both will enjoy it more!