The error dfu-util: No DFU capable USB device available remains to be the problem.
One possible solution would be to take advice from arduino support
dfu-util: No DFU capable USB device available
Upload error: Failed uploading: uploading error: exit status 74
dfu-util: No DFU capable USB device available
Upload error: Failed uploading: uploading error: exit status 74
This error can happen if the IDE could not find the selected board on the port, or if a port is not selected.
Make sure the board is connected to your computer.
Make sure that the right board is selected in Tools > Board.
Select the board in Tools > Port.
For step-by-step instructions, see Select board and port in Arduino IDE.
If you can’t find the port, see If your board does not appear in the port menu.
Make sure the correct port is selected in Tools > Port.
Close other instances of Arduino IDE, serial monitors, and other software that may be blocking the port.
Restart your computer.
See Find and stop process blocking a port.
If that does not yield something usable, I plan to seek help at
http://sourceforge.net/p/dfu-util/tickets/
unless someone at Blues can find the solution (I would not like to be a bozo Blues user going to dfu-util without knowing that it is necessary to do)