I've just joined this forum because I know how frustrating chin and jawline acne can be!
I've successfully got rid of all my acne (mild) by doing a 'candida' cleanse. You basically cut out all yeast, sugar and most dairy...
There are LOADS of suggestions for jawline acne, especially in women (hormones more so than other acne in other areas)
I would highly suggest that you cut out dairy (or change to a better quality, or goats dairy). Dairy is perhaps the cause of your acne which I know sounds huge, but after battling with persistent acne in the jaw and chin for years, I looked EVERYWHERE! (although I wish I had heard of paleo/primal before)
Check out Holistic Living for Clear Skin and Happiness | The Love Vitamin. Tracy, the author of the blog has helped me tremendously and it's because of her that I ended up on here!
I follow a candida/paleo diet fairly strictly with absolutely no dairy (except eggs), no sugar (except low sugar fruits), and no grain whatsoever.
Digestion is also key when it comes to acne, but since so many people cannot digest (low quality factory farmed, pasteurised heat treated, hormone ridden, antibiotic dairy), this could be your issue.
Seriously, check out thelovevitamin and do a quick search with "dairy".
Hope this helps!