Re: Overbite and small lower jaw
You are dealing with a very complex problem and decision - I know b/c I have gone through almost the exact same thing. I have always had an overbite and pushed my lower jaw forward when talking and smiling. So you are right to be hesitant about orthognathic surgery.
Orthognathic surgery can be done where instead of the entire jaw being broken near the ears and then moved forward the jaw is broken on either side of the chin and just the chin is moved forward. This will correct your profile but not affect your pushing your lower jaw forward and it should not affect your bite, however, it can also make a crooked lower jaw appear more so - this is what happened to me. I had an overbite, had braces and ended up with a receded chin - then had the chin augmentation surgery to make my face look better. Which it definitely did. It was done by a former dentist turned plastic surgeon so I figured he knew what he was talking about. Unfortunately, 15 years later I now have severe tmd - the term usually used to describe tmj symptoms resulting from muscular problems.
As you probably know the jaw and neck work very closely together and when they don't, tmj symptoms (jaw/muscle dysfunction, facial pain, etc.) as well as upper cervical spine (neck, shoulder, etc) problems can develop. The problem really comes from the length of your upper jaw and the length of your lower jaw and the position or location of the tm joints near the temples. When this relationship is not correct it strains the upper cervical vertebrae, mainly the C1 or atlas - which is the vertebrae the head rests on and is balanced on and can cause it to slightly mis-align - probably the reason you have the neck and shoulder problems.
The only non-surgical procedures I know of to correct a jaw that is too far back is the use of repositioning splints or orthodontia. These procedures will also change your bite. But if its not comfortable to begin with this might be the way to go. Again this is tricky b/c changing the jaw position will also affect the upper cervical spine. And as you rightly question - will this cause even more problems down the road. I have been wondering this myself - if perhaps the braces and chin augmentation did not cause the tmd I now have.
You need to find a very experienced dr trained in this area - either a tmj specialist, or oral surgeon or orthodontist who specializes in tmj. Some oral surgeons actually do the chin augmentation procedure as well - I believe that is where it originated from and plastic surgeons just picked up on it for the cosmetic benefits. Go for several consulations with different drs - you will be amazed at the varied recommendations you will get. Make sure you explain the position you have been keeping your lower jaw in so they fully understand what the issue is and that this is not purely a cosmetic issue of making your face look better. They need to determine if your jaw is actually too far back or if this is something you do just for appearance sakes.
I know my response is long and probably convoluded - your thread hit a nerve with me b/c of what I have been through - I just don't want anyone to go through the kind of suffering I have had the past 2 years. Hope this helped - even if just a tiny bit.