Keep pushing forward, valiantly forge ahead!
In that last painting, especially with the people, it would help to establish a fuller range of values.
With linework and traditional drawing and all that jazz, if you're having confidence problems, try spending a while and drawing a more developed piece, really paying attention to what you draw.
A great exercise that has helped me a good bit is to take a film you like, pause it on a scene that is really cool or brilliantly executed compostion-wise, and take an hour or two or three and just draw it, getting all the forms and values right.
Keep it up!