On the 2000 Jeep Grand Cherokee the # 15 fuse is the IOD circuit. (Ignition Off Drain) The # 12 fuse is the power windows. Both fuses are 50 amp.
This IOD fuse #15 powers the distribution box that contains the 50 amp fuse. Pull each fuse in the under hood.
Pull each fuse in the under dash. Check for on the passenger side floor is an additional fuse panel.
Before going to far suggest at night checking for any lights lit. The draw is about right for a small light bulb.
Typical draw for parked car is around 100 milliamps
Suggest that you disconnect power to the car for several minutes. Reconnect the battery. The object is to reset the body electronics module.
If the computers in the modules get a glitch they can cause a drain. By cycling the power, disconnecting battery, they will reset to factory settings. Reported it can take up to 20 minutes for the circuits to drain before you can reset!.
The Jeeps have several modules that can cause a drain
Jeep Grand Cherokee WJ Electronic Control Modules
the following web site does a great job of explaining all that is going on. What appears to be simple to troubleshoot is not so easy. He comments about delay before sleep are important. Testing after overnight may result in a different drain rate. Make sure that your battery meets specifications. In 2000 the drain rate may be relatively high and the reserve capacity of your battery low.
Hope this helps?