Hey Savethebullies
I've been reading this thread for a while and thought I'd post.
I will start off with the prong ... I use the prong collar, and I like it better that a lot of equipment. If used correctly it can be a very effective tool. However, when beginging obedience (or starting any training for that matter) there a set of "rules" that those who use adversives follow. The first period in training - the learning phase - should be nothing but positive. The dog doesn't know what is being asked of him or her, and therefore shouldn't be corrected for mistakes if it doesn't fully understand the concept. Once the dog has fully grasped the concepts, you can, if you wish, add corrections (the correction phase) if you are comfortable with this type of trainning, and from there you move to the proofing phase (ie. distraction training).
I understand where your frustrations are coming from, I've had very stubborn and high strung dogs to deal with, but the most I've ever used to "teach" them was my hand, either guiding their legs to the position, or giving them a little push from on top while guiding them down with a treat (this doesn't work on a lot of dogs as they resist the force, but if done gently can produce results). Yes, what you have done with the prong has worked, and yes adversives can teach as well as positive motivation (IE. Doberkim using the E-collar for recalls), however, depending on the sensitivly of the dog, may produce results that are undesirable tempermentally. However, if you have a fairly stable dog, you can get away with it. I just hope that if you come to another "wall" in your training, that perhaps you try out some other methods first before "teaching" with the prong ... I'm sure that there is something that will get your dogs attention and motivate him.
My concern here would be that you have a high strung dog who could be hyperactive, and needs more "attention" training before you progress with FR and obedience. It also sounds like he really hasn't been proofed enough to bring him out to a field to train. In a quiet room, with no distractions, teach the "look at me" command. Start off showing the treat right to him then bringing it to you face as you say the command. Increase the length of time that he needs to hold the "look" - reward from your face (even have the treat in your mouth and drop if to his), not your pocket. When he gets good, move to more distraction, then more working your way up gradually, when he gets really good (underdistraction), phase out the treats. This can be done with a toy as well. Dogs in these types of sports really need good handler attention, and this could help greatly with your attention problems that you are having. I would also go back to basics with the "down" command. Try again, under absolutely no distraction, and working slowly up as you see progress. I realize that he can do it at home, but if he can't do it in the field, there is a missing link somewhere here, hence going back to basics to go over the training and complete what was missing.
Have you tried different motivators? Instead of treats use a ball, a frisbee, a tug rag something that gets him excited (I'm sorry if you've mentioned this already ... its been a while since I read the begining of the thread).
You really need to get him excited about you, and not what's around him, so if you can use a toy as a motivator, don't throw it as a reward, but rather, let him tug on it. For my dogs, a toy reward is the ultimate, and produces major intensity, and builds up extreme drive. Toys can be extremely valuable tools in these kinds of sports.
Overall, I hope you're having fun with the training, keep us updated on your progress. hope this helps a bit ... GOOD LUCK!!
EDIT:
Just a thought, can you pinpoint exactly what is distracting him and use that to your advantage?