Ok another atempt
With the VM image you had before downloading this one, do this:
Boot the vm normally and press ALT+F1
user: root password: notforall
Type this
nano /etc/udev/rules.d/70-persistent-net.rules
and go to the second line, and in the very end of it change wlan1 to wlan0
press ctrl+x and press Y to save the changes
after type poweroff
(all this with the wlan card plugged in)
Re launch the VM and tell what happens please
OK, so now the 3DS connects with full signal and the VM outputs this
Also there's a green light flashing on the 3DS after some time, so I guess it works now?
EDIT: Yeah definitely works. Just checked my notifications and the 3DS has fetched 15 people on my Pokemon Y. Thanks a lot