Quoting from: Failed to load DMC firmware (more info requested) - #3 by MrChromebox
the error is normal / to be expected
Ignore the error. I would say that it is not the problem.
I think Purism would do themselves a great favour if they could get this error message completely suppressed - as it is an indication of success not failure. 
What I would do is remove the drive, put it in an enclosure, and mount it on another computer.
Then you can
a) get those screenshots, and
b) more importantly possibly fix up whatever has happened, or
c) save your personal files in preparation for blowing it away and installing again from scratch.
An alternative line of investigation would be to live boot the operating system from a USB flash drive.