Getting law enforcement officer jobs is becoming more and more competitive. Any red flags can hurt your chances of getting hired with some agencies. Having a bad driving record can hurt your chances of getting hired. However, what you wrote won't prevent you from ever becoming a law enforcement officer. Your chances of getting hired could depend on things such as what agency or agencies you apply with, when you apply, how well you do on written tests and during interviews, and how good a candidate you are otherwise. Do whatever you can to make yourself the best candidate that you can. Consider getting a college degree if you don't have one, don't do anything illegal, maintain a good reputation, keep a good driving record, don't get bad credit, improve all of your communication skills as much as possible, practice to improve your observation and memory skills, and become as physically fit as you can. How well you do on written tests and during interviews can be very important when trying to get law enforcement officer jobs. Make sure to prepare for any tests and interviews. Consider local, state, and federal jobs. Best of luck!
If you were entitled to disability benefits while a ward of the state then the state was your payee and used the money to cover the cost of your care. There is nothing due you; there is nothing to "get back." The cost of caring for you far exceeded any benefit you got from social security.
Regarding gun ownership - if you have a mental issue you cannot own a gun - whether you have or had a guardian or not.
Any attorney will do - doesn't have to be one who specializes in disability issues. Either you have become mentally competent or you haven't - and given your questions and the manner in asking them, it doesn't sound like you are mentally competent. You will need someone who specializes in mental health issues certifying that you are capable of managing your life and money.
If you are currently entitled to disability benefits and have a rep payee then the rep payee is going to have to be agreeable in your obtaining an attorney because the rep payee is the person who decides how your benefits are used. If the rep payee says no then you aren't going to have any money with which to pay an attorney.