Seriously dude, chill out a bit, there is no need to go crazy like that.
I still think you should have found a way to give this AP an ethernet connection just for this setup phase, it removes a whole layer of unneeded complexity.
I could see that my CPE510 was connected to the router that had internet by checking the other routers admin panel, but the CPE510 would not connect.
There could have been bugs in the wifi driver maybe, but I doubt it.
What was the network config in the /etc/config/network ? What was the subnet it was trying to connect to?
If the device was connected through wifi but not connecting then your network config for the "wan" interface should be adjusted.
Also, if you are connecting to a subnet like 192.168.1.X and your "lan" interface is in the same subnet (ie. it has IP address 192.168.1.1) then it's not gonna work either as "lan" cannot be in same subnet as "wan", change the "lan" IP to another subnet.
It's going to be a long wait, as this device is in a taget that won't be built for the next release as it is too new or something (yes I disagree with their choice, not that it matters much).
I suggest you set up a Linux VM (Debian or Ubuntu is fine) in Virtualbox or VMWare Player and use the Image Builder to assemble an image with the packages you need. https://openwrt.org/docs/guide-user/additional-software/imagebuilder
Since it is not compiling but just downloading pre-built packages from the download servers it does not need a powerful PC, nor it will take a long time.
You will need the "image builder" from the "Supplementary files" at the bottom of here https://downloads.openwrt.org/snapshots/targets/ath79/generic/
The command to have it build an image in your case is
make image PROFILE="tplink_cpe510-v3" PACKAGES="ca-certificates bridge htop nano luci-ssl luci-proto-relay"
Yes I added more than just Luci web interface. Especially "nano" that is a much more friendly text editor than vi. I hate vi.
It also contains Luci-ssl so it's the safe web interface over HTTPS, your browsers will complain because it's using a self-signed certificate, but random people won't be able to sniff your password with packet capture.
Now, I understand that you aren't in the best shape to do this right now, so I've built an image with that command myself.
There are two images, a factory one and a sysupgrade one. Plus some text files for the shasums and packages installed.
DISCLAIMER: I DID NOT TEST this image as I don't own the hardware. If you use it you do so AT YOUR OWN RISK. I just ran that command, if something is wrong it's not my fault.
(Note: I didn't do this "just for you". I keep all my devices on snapshot, every few months I rebuild a full firmware image like this and send it over, so I have everything set up already)