Firstboot wont reset OpenWrt

so no other way?
is my router a brick now?
how can a router with root access in failsafe mode be a brick...
there must be another way. no?

If you can't do anything in Failsafe mode, having root access is a moot point.

I've done TFTP recoveries on Archer C7 V2s dozens of times, and the process works...unless the wrong image file (upgrade instead of factory, or the wrong region) is used...or there has been further damage.

What is the exact name of the file you renamed to archerC7v2_tp_recovery.bin?

You should have used a squashfs-factory.bin image file.

Is your C7 V2 a U.S. or EU version?

Look at the sticker on the outside of the router.

If you got an image file for the wrong region, it won't work.