Brake line connection

[Droff]

I have found a brake fluid leak on the rear driver's side brake line of my '68 GMC 3/4 ton. It's leaking at the spot where the tubing comes through the flare nut, can't get it to stop. I had a plan to remove this line and either replace it or re-flare the current line. It's a new wheel cylinder.

There's a tee block on the rear axle that feeds each side of the truck and I can't get the line to break loose of this tee. It's been sprayed with PB Blaster for a few days but no luck yet. It feels like with more torque on the nut, everything will twist up into a nice little piece of scrap metal. I've got a wrench on the flare nut on the pax side to help with this but neither side will move.

Anything I can try in order to get this broke loose? It isn't rusted.
Thanks.