To start hydraulic clutch systems like the one in your rig are not adjustable. If the disc is warped or falling apart you likely will have a heck of a time getting it into gear because its dragging on the flywheel or pressure plate when the pedal is pushed to the floor. If its worn out a giving it 100% gas pedal in 3rd or 4th it should start slipping and the rpm will go up with no acceleration of the jeep. The drag feeling?? Drive it for 10 or 15 minutes down a open road, slow down with gears and use as little brake as possible. Pull over and feel each wheel center area for excessive heat in comparison to any other wheel or wheels. It could be a hanging up E brake cable , hung up caliper, broken rear brake hardware as in return springs,adjusted incorrectly, mud caked backing plates and that sort of thing. It might be worth your efforts before you even take off again to jack each wheel up and spin it to see there is any abnormal resistance which goes back to brake issues likely. Regarding the E brake cable set up. being your lifted and not knowing the history of things or your ownership, I take a close look at how bad if any, the E brake cables might be. There isnt a whole lot of slack in them and it seems on some years Ive owned and going lift with full drop of one side will tax whats there cable length wise. Let us know what you find if you would as we all learn from others sometimes out of the ordinary problems.