Searched the threads and can't find what I'm looking for although now I'm wondering if there's another name for the pulley I'm looking at. I'm needing advice for my 89 s10 blazer with the 4.3L (auto, 4x4 if that's necessary info)

Couple nights ago I hit a decent pothole pretty hard (live in good old Washington state, thought it was just a puddle so didn't think about it) popped my belt off the idler pulley (the one below the a/c) but managed to drive it the 18mi home and back to work the next morning with plenty of squealing. Had to work on it during my break, belt looked fine but replaced it anyways. Noticed the bearings in the alternator pulley were going(hard to spin) replaced that too. Noticed the belt is on the very edge of that pulley it slipped off of but had to go back to work.
Everything was fine til I had to go thru a huge puddle to get home and it slipped off again. The rain has been relentless so there's no way to go around the water. That idler pulley is free spinning, nothing is holding it up other than it's not aligned right and considering replacement but wouldn't that just seat it in the same spot? I've looked at everything and that is the only thing off. Haven't had to do much to this truck and my second car is currently down (getting rid of it and haven't had a chance to go car shopping - go figure the truck starts needing work) i guess is there a way to align it or do I need to go and buy a new one?

Also can anyone recommend a repair book for this truck? Got a chiltons and it's absolutely useless for anything remotely specific.