Typically somewhere between 15 and 20 psi for all Jeep 4.0's if its under 13 you have a vacuum leak for other issues
No, it doesn't.
It begins at the intake manifold.
look on the manifold it should have the squence engraved on it
Check the vacuum operated valve at the hose going to the heater core.
YES
No, it uses a MAP sensor (manifold absolute pressure)
where the intake manifold attaches to the head, and along any of the rubber hoses that are attached to it.
the vacuum hose connects to the airbox
At the rear of the intake manifold right next to the distributor cap.
Need a special socket. They are located in the exaust manifold(s).
The intake manifold, on your Jeep grand Cherokee, is located on the front side of the engine. The exhaust manifold is bolted to the engine.
It is on the right front corner of the intake manifold. It has two wires and points out at a 45 deg. angle.