His fate:
I hope he somehow escapes the planet intact. Perhaps in an escape pod from the Derelict after infecting the pilot.
Drifting off into deep space. Trapped with his thoughts, slowly going mad.
Until his pod crashes on some other planet. Cue David spin-off movie.
His relationship with Shaw:
David was gonna kill and cut up Daniels. The same thing he did to Shaw.
He used her and killed her when she was done being useful alive.
Yeah, he could keep her alive for a certain amount of time during and after removing parts. But sooner or later that person dies as consequence of those operations. I think that would counts as killing.
Ridley Scott said in an interview that David hates humans and the Engineers (=humanoids).
Shaw was a human.