[General Questions and Answers] enoli:
Help with LG G3 Turns off During Boot & Unable to Factory Reset (is it a lost cause?)

Hello everyone. This is kind of a complicated issue, and I would love any help I can get.

Back story:

I have a Verizon LG G3, purchased in December of 2014. I never rooted the phone, so it has been stock this whole time. A couple of months ago, the SD card holder randomly stopped working (no spills or drops). I tried multiple, new SD cards, formatted them and everything, but the phone just kept ejecting the SD card, and corrupting them, so I just gave up on it and stopped using an SD card in the phone. This is not the current issue at hand, but I wanted to preface that I've been having issues with the phone.

Fast forward to a month ago. I had my phone plugged into the wall charging, and was not using it. I noticed out of the corner of my eye that my phone turned off. I unplugged the phone and tried turning it back on. It showed the LG logo screen, then the verizon screen, and then just turned off. When I tried powering it again, it did nothing. I pulled the battery, put it back in, and pressed the power button. I got the same series of lg logo, verizon logo, then off. I thought maybe it was a battery issue and took it to a local phone repair shop. They put in a new battery, but got the exact same boot problem I did. I left the phone with them, and they took it apart to see if it was a hardware issue (and the infamous stuck power button issue). When I returned, they told me that they did not find any hardware issues. It also was not an issue of the stuck power button/power button not working. They decided that it must be a software issue. Their explanation was that the phone had probably tried doing a software update and something went wrong. They said they could only fix it by completely wiping the phone and installing the software back on. I was reluctant to go through with it because (1) I would lose all my data (and I did not back it up, my fault, I know) and (2) it seemed like they wanted me to pay almost 100$ for something I could do at home. So I kept the phone and left it alone for a while. Now, it has been a month since the issue began, and I'm trying to see if I can fix it. Here is what I have tried.

1. Tried to power it normally again, but now the phone won't boot past the lg logo screen (no verizon screen, just turns off)

2. Held down the power button and volume down button, and able to get into recovery.

3. Tried safe mode -> boots to lg logo and turns off

4. Tried wipe cache -> boots to lg logo and turns off, does it twice

5. Tried USB debug -> shows the android icon, looks like its working, turns off

6. Finally tried factory data reset -> goes through the "are you sure" screen; select yes; shows android icon, looks like its working, turns off

7. Tried holding down the up button and plugging it into a computer to reinstall firmware, shows logo and turns off

8. When I plug the phone into the wall, it charges normally. Simply won't turn on past that.

I'm not sure what else I can do to the phone. Is there a way to factory reset from a pc or mac without the phone being on? Will I just have to take it to the tech store so they can do whatever magic they seem to possess? I already plan on never getting another android after the issues with this phone (and many androids before this one), but I need this phone to last until December.

Sorry for rambling and thank you for any help!