Going on the bit isn't a head position, its a way that the horses body works. Getting Nugget to lower is his head will not put him on the bit. You ideally want to get him moving forward into the bridle and seeking the contact from behind. If you are not experienced in this the best thing to do is to get a good dressage instructor - they can make a world of difference. I don't think I am experienced enough to explain it all in detail, but I am sure some people will, but seriously consider getting a good dressage instructor, they can help you improve so much.
If Nugget isn't used to traveling in that frame it will be difficult for him to maintain it. I've heard a fair bit of bad things about side reins - its generally quite a controversial topic, but unless the horse is used to seeking out the contact they can do more bad than good. I wouldn't recommend that you use them.
Have a look on
Horse Problems . Its a decent Australian (like us) site with some good advice from a popular trainer. I believe the guy talks about runnings reins or something on the lunge and they could probably suit you a lot better than side reins.