How can I reduce or lift these jowls and slim my lower cheeks/jawline?

Thank you for the question Emily. 
It is hard to give a comprehensive reply to your question since only a portion of your face is visible, and I am missing the details of your age and other information. 
In my practice what I have found to work well, for women who have high cheekbones and fullness in the mid face, as you say you do, and who are in their late 30s and up, are thread lifts using threads of different compositions. 
They lift the sagging skin and reposition the tissues during the procedure itself. Over time, as the threads are dissolved under the skin, they stimulate your own collagen production, providing subtle lift to the area of concern. Depending on the type of threads use, results last from 12-18 months or longer. Average cost is around $3000 and up, depending on the number of threads used. 
Alternatively, if the sagging around the mouth is from lack of volume around the ears, filler to this area may help redefine the lower face better. I typically use 2mls of filler or more for those, again dependent on the individual face, and cost is around $1300.