Remember that part of the exercise is to draw confident lines from the shoulder, using the whole arm. You can see on e.g. the mint box that the lines are a bit wobbly, try to avoid that by making a single quick stroke all the way. See the video on line quality: https://www.proko.com/course-lesson/6-habits-for-good-line-quality

No worries, Itswalker. Please don't feel you need to match the reference exactly. When we practice drawing from reference, we are interpreting the image, so there will always be slight differences between your version and the reference. I tend to make the heads too big myself, and it's something to be aware of, but I think the head in the reference is a bit larger than normal proportions anyway to fit anime/manga style, so you might have been unconsciously adjusting that element to be more realistic (or heroic, because smaller heads are usually associated with heroic proportions too) without even realizing it! I think it's important here to concentrate on the strengths here too. I'm impressed by your attention to negative space. Two areas that really stand out to me are the curve formed by the belly and the raised leg and the knife arm, back, and weight-bearing leg. This practice is challenging, tough work, but I can see by this great focus that you are well on your way as an artist. Keep on practicing and growing, and who knows what amazing things you'll do in the future!

The shadows look nice