Booster/vacuum issues have no effect on basic braking, other than making pedal pressures for a given brake force lower.
Since you have NO brakes, you can dismiss them as an issue.
Let's start with the basics---is the master cylinder full of GOOD brake fluid? Have you tried to BLEED any of the brakes, and if so, do they bleed normally?
1992 XJ 2" lift -- RIP
2000 XJ 3" lift -- Australian Ford Big Brakes up front, rock rails, ZJ rear discs (with WORKING parking brake), C4x4 rear bumper/tire carrier, Hella H4 headlights, IPF driving lights, OEM skid plates, OME springs/shocks, JKS LCA's, JKS Sway Bar links.