Wow!
1. Speak to your administrators about the classroom behaviors. If you get no support (as was my case several years ago), you're going to have to carve out your own empire (suspensions-referals-suspensions!).
2. These kids have issues (obviously), and if you establish some behavioral expectations, they'll test them, but eventually they'll comply.
3. Being "nice" is different between your personal life and your professional life. The students need boundaries, and clear expectations. If you are consistent (tough, but not a bully), you'll be able to turn things around a bit.
4. Some kids (like some of the respondents) just have to take out their frustrations on whoever they perceive to be a handy "mark".
ALWAYS remember that you are a professional, and comport yourself as one.
5.Put out some feelers in some suburban/rural districts. You will encounter the same types of problems there, if you don't quickly, and decisively establish yourself as a tough, consistent professional with high expectations, and the resolve (caring) to see the students succeed. You absolutely MUST do this at the BEGINNING of the school year, and work hard to keep this going until June.
6. Take some time for yourself:
*Work out
*Martial Arts (VERY relaxing, and inspires confidence)
*Pray/meditate/seek counseling to calm your nerves.
**You don't have to become a Bible-thumping fanatic, or some kind of ultra Seishin Zen master; just take a few minutes after your workout to "chill".
7. Good luck, and please let me know how things work out for you.