yet, lots of weirdness. In general you have approached this with a bit of a photo-shope type mentality, which doesn't work well with parametric modelers.
you do have a pretty decent end result, but at the cost of being able to easily edit and make changes. I suggest the following-
-keep practiceing.
-model around the origin. try to use the origin planes for symmetry.
-to make changes, go back to the originating feature in the time line.v(ie-learn to use the time line)
-DON'T USE THE MOVE COMMAND. like, ever. it's evil.
-learn how to use components. they can be tricky at first, but when used right it makes everything easier.
on this model I think things really when south on you when you made the chin piece into a surface body instead of a solid(I guess by deleting a face in surface mode. donno, didn't look into it that far.
here is a long tedious screen cast of me fixing your model. didn't know what I was going to do going in, so there are some missteps. the main thing here is I turned off the history so it would be a DM model instead of parametric. you lose the timeline when you do this, but in this case the timeline wasn't useful anyway.
resulting file also attached.
