Default soft brick recovery problems

hello xda community
i've installed g3 cloudyflex on my g2.. and after wiping cache the device was basically soft bricked (lg logo loop)
now i've tried to get to back original kitkat rom.. everything went fine but then the device got errors "Unfortunately has stopped" and some other gui errors.. the screen is black but you use power/vol buttons for reboot etc
i couldnt get in my device so i tought of a hard reset...
but the psyhical button one doesnt seem to be working for me.. what to do??... not possible to get into rec. mode from pc?

after some time it manages to get to usb screen but it crashes completely and the device shuts down
also i cant get into safe mode as it keeps rebooting until i release power button

tldr: How can i fix my g2 if software and back button recovery method isnt working?