I don't think quitting job for steemit is a good idea even your income from steemit is high. I do not want to be that pessimistic, but steemit is a new social media, no one know if it can continue running in the future. Say it will run at the following 5 years and you don't have a job and investiment to support your life, it will be horrible as you are not able to find a decent job because you are out of the market for a long time. You should treat steemit as a part time job for extra income only.