You've already "got" Harvard. HarvardX won't clean up the stain of 3.0 any better than SB can. Go home and save money.
You'll want to follow the same low GPA advice as everybody else. A Harvard 3.0 doesn't beat a SUNY 3.5, for instance.
Point being, you should be looking at a 2nd bachelors at SB. You need a whole lot of A's.
Best of luck to you.