The brake lights do not tie together.
Left and right run individually to the lever switch
except that at the brake light switch, there's two wires attaching, but one goes straight to the lights themselves with a wire connecting it to the flasher, then the other goes to the fuse block, then to the light switch on the dash.
the firewall switch should have the black/grey wire on one post
And the power on the other.
Sounds like your close just need to trace things out
