Electrical issue?

I have a 2000 WJ that ran fine when I parked it. It sat for 6 months as I just took to using my XJ. When I went to use my WJ it refused to start unless I gave it lots of gas, and would idle extremely rough, stalling out if I didn't sit giving it gas for a period of time. Eventually it would stay idling without me having to constantly step on the pedal. Once I attempted to drive it, it's extremely sluggish and unable to get any speed going, almost like it's in limp mode. When I try to accelerate, the radio shuts off, the odometer blinks on and off, the ABS light comes on, among other lights, generally things just go haywire electrically. I noticed that the volt gauge reads 9v all the time, even with the key on, engine off. I put a new battery in and checked the connections, the multimeter reads 12.6. When fiddling around on the engine while it was idling, I unplugged the field wires to the alternator, and noticed it started idling perfectly. Plugged them back in and it started idling really rough. Unplugged them again and it drove fine around town on just the battery. So, I took the alternator out and brought it to an Advanced Auto to have them test it. They said the alternator kept blowing the fuse on their machine. I bought a new alternator and slapped that on there. The same issue persists. Volt gauge still reads 9 even with the engine off, which I thought would just show battery voltage at that point. Any insight would be greatly appreciated.