Cutting Land; Help with Planes

In the "Help Land" Image: How would I make the red part while leaving the blue line to "attach" the two. I have tried a few different plane configurations but can't get it.

In "Help Land 2" Image: Is there an easy way to have the top surface (an extrude boss) "even" with the highlighted face? They are 2 separate extrusion (the blue is extrude boss the highlighted extrude cut)