Well that looks good so I'm at a loss for why you're having such strange issues. The fact that you had issues straight away during the initial setup is concerning.
If I were you I'd reinstall the firmware but do it through the GUI (Administration - Firmware Upgrade). After the firmware is uploaded the router will reboot and go into the initial setup again. At this point don't do anything, just leave it for a couple of minutes. Then press the reset button (not the WPS button) for 10 seconds and wait for it to boot up again. Now see if you have the same setup problems.
I know you've done this before, but it's worth trying it again just to be sure.
Before I read your post, I just cleared NVRAM by holding the WPS button in and powering it on, to see if that made a difference. I still had the same problems during setup. (I did use the reset button before, by the way.) If I try to enter the SSID and passwords for the 2.4G and 5G connections, I get the spinning dots. I even left it for 10 minutes or so, but there's no progress. the only way I can continue is if I click next and allow open system connections, then quickly change it in the main menu.
I checked my NVRAM usage before and after entering the SSID information, and it stayed at 63%. I tried uploading the .ovpn file again, and a few seconds later, the page refreshed and it was gone. I checked the NVRAM usage and it was now up to 67%. Strange. I'll try reinstalling the firmware again tomorrow using the GUI, to see if that makes a difference.