First well done on taking on such a huge thing a female full figure, and I think you have done a nice job so far, and glad your looking for help to push it further . While I could critique your sculpt directly I feel it would more beneficial to cover some fundamental things that will help you much better, some things that I wished I was told when I was at your level some time ago. Because you will start from scratch tons of times as you get better there is no point at this stage to pick bits here and there, as your find once you get stuck into anatomy your change everything a tons of times as your progress.
Anatomy when using a reference without proper foundation understanding of anatomy leads us to simply copy what we see, and leave out what we dont which is not a good thing. The foundation is always the Skeleton, and its so essential you know this.
The skull itself has 8 main bones that you should be aware of, and within this you then have its proportions which set out where certain features are placed in relation to each other. Study the skull, and understand these things. As an example different parts of the skull will face is different directions from each these are called plan changes and from these changes t will dictate how light effects the surface of forms.
Once you get the height and depth of the head and its features in place, you can use this as a Unit of measurement for the rest of the body. An average woman is between 7 and7.5 heads tall. Use a basic canon system to help get you to average then you can break this after. This average will in time internalise, that means it will become part of your natural ability to instantly see whats wrong without measuring anything. Half a head unit can make up the distance between the chin and sternal notch, the slight indent you see btween your clavical. Your clavicle of some people can look very straight from the front, but from the top like a set of handle bars, if this is done right this set you up for getting the neck in the correct place. At the end each each clavical its connected to your scapula commonly called the shoulder blade. This part of the shoulder blade is called the Acromium process and is flat and never has any muscle covering it, this set ths placment of the three heads of the shoulder muscles (deltoid)
From this small area I hope you can see that the correct placement of one part set up another, and on it goes. Get the skeleton right, and the limbs the correct length then your be set up for placing muscle, the fat. Here is a guide I made which details some of these things.
I will come back tomorrow and point some areas out on a basic level that will make the biggest differences, but this is only a temporary short cut to the essential things your need to cover over time, this is why I recommend doing just heads for a while as to give this area its full attention.