You're making a lot of progress! I can definitely see a lot of improvement.
I think one of the main issues is that you're trying to go too fast. Try to slow down in the beginning and analyze what you're doing. You're talking about working on the mouth but you still have questions about the basic head structure and nose.
Aside from that, here are a couple of points for the proportions:
1. It's great to see that you've started drawing the cross, your circles look a lot better. But be careful because you're mistaking it for the eye line. Once you draw it out, erase it and then start drawing the lines for the head.
2. Remember the line in the center of the head indicates the middle. This includes the middle of the chin. It took me a while to realize this when I was learning...
3. Follow your guidelines. The nose should be within the lines.
4. Remember the side of the face is flat, so the edge of the circle should be cut.
Your noses aren't that bad, it's the construction underneath. I took the same nose you drew and placed it in the correct proportions.
It might help to draw over a few pictures of heads like you did with the body earlier.
Hope this helps!