Yes you can but don't quit your day job just yet!
Your post says you've been a hobbyist. What sort of work have done, have you sold any of your work, and done it at a profit? By profit I mean have you figured in overhead, electric, fuel, cost of work space and materials and so on? All of this and more are costs that have to come out of your selling price before you make any profit. How about health insurance and cost of advertising or building a website?
I'm not trying to be negative here, I'm trying to point out just some of the things that are important to think of BEFORE you jump from the kettle into the fire of self-employment.
You ask in your post what kind of blacksmithing you should do make a living? Well that depends on YOU and the market out there. Do you enjoy production work? If so then maybe selling small items on Etsy will fit the bill. If not then that may not be the market for you but all forms of smithing are going to require some sort of repetitive production.
I suggest before you leave your current job that you do some research. Look at numerous websites of professional blacksmiths and see what they offer to their market. If you see smiths offer work that interests you ask your self am I qualified and skilled enough to do this type of work. It takes practice and patience to gain the skills needed to satisfy customers and gain repeat work.
If you find a type of smithing that you'd like to pursue and don't feel you're up to it check out some craft schools offering courses in what you're interested in. Join ABANA and a local affiliate, get to meet professional smiths to talk to. ABANA also offers scholarships to take classes.
My final word of advice would be : Start slow keep your current job while building a blacksmithing business working evenings and weekends. If this seems to take to much of your time please know that most professional smiths are working sixty or more hours a week to stay afloat.
LASTLY Don't think I'm just a key board junky who wants to hear himself spout off about business. I'm 76 years old and have over 50 years experience as a professional blacksmith and teacher.
I hope what I've stated helps you to make a successful choice.