Ok.
So I got the right part from an alternator repair place nearby. Seemed like I'd get better quality than the $5 part.
I charged the battery and installed it and my readings 13.3 to 13.9 (12.8-13.3 before I add .5 v) depending On whether I'm Idling or driving.
This is basically the same reading as before.
So far the check engine light is still off after 20 minutes of running.
I also replaced the windshield washer fluid sensor. Which apparently is the reason I got instrument cluster failure warning.

Would a squeaky belt affect voltage?