is my harmonic balancer bad?(99 buick century)

What is your question?

Hey guys, so I have a 99 Buick Century and have two questions. Recently check engine light come on, plugged my OBD II and it said it was the crankshaft position sensor. I first like to understand how there is 2 crankshaft position sensor on this car... one is plugged into the back of the block and other one seems like just some kinda harness that attaches to the front of crank pulley. I replaced both anyways just so I can get the code away. Now the code is off.. but my car vibrates like crazy, just going past 25mph it gets scary so I had to park the car right back. To get one of the sensor off, I pulled the harmonic balancer off since it was necessary.. I used proper tool for both removal and installation, I don't think I stripped the crank threads, at least not that I see or feel. I have two, maybe three questions... here is some pic of the balancer I pulled off. Before this job, the car had the engine code but no vibration, so I don't think the balancer is physically bad but wha