How can I align the PCB and the polygon?
It really doesn't matter if the drawn polygon "slops outside" the PCB dimensions &mdash; the actual "pour" that gets generated will be constrained by the design rules to some setback inside the edges of the board. You'll see the actual generated shape if you run the ratsnest command.

Regarding your other errors, you really shouldn't have the layer with the drawn dimensions, arrows, etc. in it selected when you run DRC. Select only the layers that will actually be used for the fabrication. Also, you should not be putting that kind of documentation in a copper layer (Layer 1) in the first place. 

In fact, I tend to run DRC on individual layers, one at a time, to get rid of most of the initial problems, before running it on the whole set to catch the inter-layer issues.