Those cheap flaring tools aren’t suitable for steel, generally.
Get underneath with a torch and follow the original pipe to the ABS unit. Thread a new length of copper pipe alongside it, to get the route correct, then make the joint into the ABS block. Cut away the old pipe before clipping the new into place, checking it’s secure and not rubbing.
A few tips:
To stop the pipes dribbling so much while open, wedge the brake pedal down with a bit of wood.
It might help to anneal the copper where it needs a sharp bend - heat to red hot then leave to cool.
Red rubber grease will help the flare form.
I’d seriously consider running a continuous length front to back to avoid having a joint. Brake pipe is cheap, brakes are critical!
Once the pipe is fitted, top up the master cylinder, release the brake pedal, open the relevant bleed nipple, put a container under it and go for a coffee. Once it’s dripping freely it’ll be 95% bled.
Be careful tightening copper pipe unions - feel the nut just start to seat, then maybe 1/2 turn. Test with the engine running and a hard press on the pedal. Nip up any unions that are weeping.
I’ve seen copper pipe unions overtightened (by a trained mechanic) that sheared the flare off, then let go under pressure.