If you can acess twrp,then connect the phone via usb cable to pc and if you set up drivers corret then you have to have adb mode!
Install sdk tools, a good adb driver,after that in command promp you can sent files via push command!
Here a link to a tutorial of setting up sdk tools
Here is a youtube video for adb pushing https://www.youtube.com/watch?v=YP1LVOKgwQM
I had similar problems with my g2 i had Twrp installed but coudn't sideload, but if you set up correctly adb then in commnad promp you will have under "adb device" command your phone and has to sad recovery then just simply push the file and good to go......