OP, you have an awful lot to work through right now. You're obviously not in a very good place and to me that says you aren't ready to be making major decisions right now. I don't say this to be unkind, merely to point out that this comment, along with several others in this thread tell me you're miserably unhappy, feel yourself a victim, have come upon a dream that you want to pursue and have decided you're finally ready to take action.
Everybody needs help sometime. That being said, you don't move from a situation where you feel controlled, unimportant, unappreciated, etc., and make your move based on planning that doesn't include you being able to control your own destiny in rather short order. You will not be able to do that based on relying on spousal/child support, assistance from your family and banking on your dream writing career. That doesn't suggest you cannot achieve your dream career, but rational thinking suggests you pursue that as an adjunct to a concrete, reliable job that you know will pay the bills. This advice holds even if you decide to remain in your marriage. If you want to control your destiny, you have to take the steps to do just that in a real way, not in a way that exchanges one controlling, unstable, unhappy situation for another. Your marriage may not appear so bleak and confining if you establish your own independence within it.