Yep on all that.
You could have over tightened the pinion nut and that will burn up the pinion bearing and cause your howling noise.
If you replaced the posi with another GM posi the carrier shimming will be pretty darn close ...What was your backlash reading?
Driving with out fluid was the big mistake on ALL the bearings...It would not have taken too long to torture all the bearings in the rear enough to have cause one or 2 to go south and give you noise issues.
THe crush sleeve is a one time use item so that was also the issue for the pinion bearing preload probably being off / too tight.
I guess that is why 300.00 to setup a rear ain't so bad when it is done right.
Bearing kit for 89.00 axle bearing and seals for 30.00
bearing kit includes the following-
2 carrier bearings and races
1 inner pinion bearing and race
1 outer pinion bearing and race
1 Pinion seal
1 pinion crush sleeve
1 pinion nut
1 rear inspection cover gasket
1 carrier pack of carrier shims
1 pinion pack of shims
1 marking compound and applicator brush
10 ring gear bolts
shipping 10.00 - Let me know.

Jim