Wow, that'* quite a sentence/paragraph! You may want to try using some punctuation and capitalization to make things easier to follow.
If I read things right, you're tracking down a squealing noise from the belt area. There are several things besides that belt that could cause this. The most likely culprit is a idler pulley. Try adding a small bit of oil on each pulley'* bearing one at a time. If the noise goes away, you know which one is bad. Replace it.
The alternator bearings could be noisy also. When you remove the belt, see if it spins freely and quitely. Do the same for the water pump, but they generally leaky first or create more of a rattling sound.
Depending on which vacuum line is leaking, that could set off the check gas cap code.
Black 2000 SSEi, Silverstar Headlights, Angel Eyes fogs, 3rd brake light overlay, hi-flo cat, drilled 180 degree thermostat, Intense FWI, PCM, shift kit, and 3.4 Pulley. Solid front mount.