Hi Lindsay. You did a good job packing your bag. And the total weight is only 16 pounds : congratulations to you. You will appreciate the low weight when carrying the pack on your back. Shirts made of material that is not cotton do not become wrinkled. But I like the comfort of cotton shirts, and cotton pants. You asked about a travel pillow. If you are talking about a neck pillow, for use on airplane seats, I suggest that you experiment with it before flying to Europe. I thought using a neck pillow is a good idea, because it has a concave shape, preventing a person's head from moving to the left or right side (and preventing neck pain). But I did not like resting my head on a neck pillow when I was seated in an airplane. The seat back reclines back a short distance (in the coach section): thus when my head was on the pillow, my head was not in a reclined position, and sleeping was difficult for me. And carrying the neck pillow (filled with seed hulls or ...) in Europe was annoying. I attached the neck pillow to the outside of my carry-on bag, using a safety pin, but the cloth tab that the pin was attached to ripped off from the pillow. I gave the neck pillow away in Germany. In many airplanes, the tops of the seat backs have a curved shape, preventing much lateral movement of a person's head. Some travelers like bringing a neck pillow that is inflated with air. When not in use, it is deflated, it can be put in the carry-on bag. I think a neck pillow is not a necessary item. But some people like to have a small pillow at the wall of the airplane, (if they are at a seat by a window), they lean their head to the side, on a pillow.
As Rick Steves suggested, a small cloth bag (micro fiber) can be used as a pillow : put a sweater or other soft item in the bag.