There is no need to repeat the previous jaw surgery. A sliding genioplasty will give you more chin projection. In men, I typically advance the chin a minimum of 5 mm and usually 7-9 mm. A 3 mm advancement is generally insignificant. The chin can simultaneously be lengthened.
Fixing your asymmetry will involve many different parts. First off, this is not caused by side sleeping, but was actually due to your positioning in the uterus before you were born. As for treating this, I would recommend a cheek implant on the right side, to balance it out with the left. Then...
Depending on how much of a reduction you are looking for (desired outcome), you may be able to obtain that with just chin/jawline contouring. This procedure essentially shaves down the bone and can contour a more defined shape. However there is a limit to how much can be removed. If you are...
