I can see in https://openwrt.org/toh/tp-link/td-w8960n that v1-v4 (and possibly v5) are "supported". Is there a build for v7? BTW, I tried flashing a few different images for it (v1-v5) through the web interface and they didn't work. Is it because they were not intended for v7, or because it is not possible to flash OpenWRT through the web interface?
you could have just as well (soft) bricked your router, consider yourself lucky.
does it say anywhere they could be used on the v7 ?
it's not a supported device, you'd be the one to find out.
for all we know, the device could be running a completely different arch,
then the supported versions.