Answered by Ustadha Shazia Ahmad
What is the status of my daughter to my step-father? Would she be allowed to be alone with him and appear without hijab in front of him?

She is his mahram (member of unmarriageable kin) and does not have to wear hijab in front of him. (Reliance of the Traveller, m6.2 (7)). She also may be alone with him.
And Allah knows best.
Shazia