You still need to observe the two-week notice

period if it is in the contract.  However you were mistreated, you don't want to burn the bridge.  You never know.  I have heard a lot of stories of people regreting what they did when they were young.
What's in the performance review - only very few people will know, so if won't hurt your reputation.  But if you leave without two-week notice, everybody will know that you didn't follow the rules.