Getting your dog to sit to whistle and face you no matter how far away he is is not as hard as you might think.  From my experience, you need to make this something that he loves to do more than anything.  Sitting means something good is going to come next.

Heel Whistle Sit

Start by blowing the whistle every time you stop walking when you are heeling.  Right after he sits, click and give him a treat.  Do this for 1 week, EVERY time you blow the whistle give him a treat, don't forget the treats.  Do not every blow the whistle during this time unless he is heeling, or in front of you.  After 1 week he should be sitting quite reliably when you stop and looking at you for a treat.  Don't forget to wait for him to sit all the way before giving the treat.  Do this BEFORE his normal food, I actually feed all my dogs food during training and they never get a normal meal.  Do not say sit, only use the whistle to talk to him.

This training accomplishes the following

Platform Training for Sit

Now place your dog on the top of a small platform. Blow the whistle for sit and treat.  Even if he is already sitting, give a treat.  Now walk around behind him and blow the whistle and pull on his leash at the same time to make him turn around and face you.  When he turns, even a little, click and treat.  Keep doing this until he turning the entire way and then sitting.  Eventually he won't sit still and will try to face you at all times and you might need to hold him as you walk around him.  Sit, Whistle, Spin, Sit, Click, Treat.  During this he is always on leash, and you are always close to him.  Once he is spinning fast, you now need to teach him to stay put when you walk around him and when you are behind him, walk back 3-4 steps, give the whistle, when he turns, click, big praise, and treat.  Keep doing this until you can move back a long distance and walk around him at any point, blow the whistle and he turns and faces you.  If your dog is lethargic in turning towards you, a few sharp leash corrections each time you blow the whistle should motivate him more to turn towards you.  Do this every day, for at least 2 weeks once a day, more often is better.  Using both hands in front of, motion for him to sit squarely, when you turn, pull on the leash.  When he is square, click, run in and treat.

This training accomplishes several things.  

Platform Training for Handl