If you have concerns about job security, you can scratch chiropractic off your list of options. I think all chiropractors will agree with me that in general, making it as a DC is tougher than every other mainstream health profession. Reimbursement and demand for chiropractic services just aren't sufficient for the number of graduates and loans accrued in chiropractic school.
The thing with chiropractors is that you have some that will practice very similarly to PTs and some that will practice very differently from PTs (i.e. alternative medicine). Those that choose to practice more similarly to PTs find it tougher to generate an income they would like. The quality of training in exercise and rehabilitation varies among chiropractic schools as well. Some chiropractic schools will also lead you to believe that you have sufficient education and training to be a primary care doctor. Invariably, all chiropractic schools suffer from a clinical education that is less than desirable. Basic sciences education are sufficient for what chiropractors need to know (if they stick with functional musculoskeletal conditions) but not beyond that (i.e. not for becoming a patient's primary care doctor). Sadly, much of your success as a chiropractor comes not from your clinical acumen but how good of a business/sales person you are.
Don't get me wrong, there are some very good, ethical chiropractors out there. However, it's a gamble. Do you want to gamble $100K and years of your life to see if you can make it as a chiropractor? Basically, until the chiropractic profession can decide what it wants to be and clean house, I would stay away from it unless you really have a deep-rooted calling to become a chiropractor and understand all the hurdles you will face. That's my opinion as a former chiropractor.