Replaced failed alternator with refurbished one and got flickering lights and also belt sound?

Replaced failed alternator with a refurbished duralast and it has worked well enough to drive but interior lights, reverse lights, and daytime running front ambers all flicker, headlights seemed to be okay from what I can tell.

The belt also seems to be making noise and I’m guessing I need to tighten it? Added a video of the sound. Hoping the alternator continues to function as it was a bitch to replace.