In what way can I fix my retruded mandible/weak chin, labiomental fold?

Any time someone juts their jaw forward and creates their desired effect, they are demonstrating that a major component to their jaw deficiency is in the vertical dimension. The key question then is whether you only want the chin changes or the chin and the entire jawline behind it. If it is only the chin then a vertically lengthening bony genioplasty can be done. But if it is the entire jawline including width then only a custom jawline implant will suffice.

your assessment is right on.  I think a partial correction would be an achievable and a good goal in your case.  A Chin could give slight forward projection, a slight vertical height correction without tweaking your mental labial angle too much.  A small( small amount!) amount of filler in the nadir of the mental labial angle could help as well. In your case as you have mentioned a complete correction would come with consequences.  Facial hair in this area helps divert the aye  and can be helpful  Best, Mats Hagstrom M.D.