Can chiropractors really help if you have chronic back problems?

Short term. Chiropractors provide a sort of stylized massage which can be comfortable for a day or two for back pain. They do not provide long term relief and are certainly not interested in cure because they want you coming back again and again. If your pain is persistent, you should see an orthopod for a better diagnosis and chance of a cure.
Yes. But in general a medical workup should be performed by a licensed physician prior to chiropractic treatment.