The address issue, alone, should not cause you a problem. But combined with the other issues, you audit risk will go up.
You'll be claiming Head of Household (HoH) in a home you don't own and were in less than 8 months with dependents you supported less than the full year.
The claim your sister, you will have to have provide more than half her support. You do not need to have provide more than half the kids support to claim them.The main requirement is that you lived with them for more than half the year.
