Is chiropractic medicine a legit treatment?

Not really. Chiropractic relies on an outmoded theory of disease causation which has been disproven time and again. Chiropractic manipulation can cause some symptom relief but can be dangerous and diagnosis and cure are beyond the practice of chiropractic. It is legit in the sense that their lobbying and legal suit actions have forced coverage for chiros in most jurisdictions.
Yes but... Chiropractic treatment helps many people, but you have to be patient and also realize that it can't help or "cure" everyone. All professions are similar in that a multi-disciplinary approach is often the best road to take in a lot of issues.