Good analysis.
I think that earning a full-time living with Steem is possible, since as you get more followers and as your steem power increases, you will tend to get a higher income from your publishing.
Also, 8 posts per day, while it seems high is doable, since it would mean spending an hour per post (assuming you work 8h a day).
Good luck!
Thank you for your comment. Well, it might be doable, but 8 hours per day is probably what I spend already.. :D - As I'm not native in English and I love steemit, I'm probably spending even more than 8 hours per day as it is already.. :D