Nasty Baby (2015) review

Hack artist Freddie (Silva), who lives with his partner Mo (Tunde Adebimpe) in Brooklyn, desperately wants a child and their friend Polly (Kristen Wiig) is willing to inseminate herself but Mo isn't sure about the whole idea - meanwhile, Freddie's video project (which he calls "Nasty Baby") gets understandably rejected by a gallery, and then there's a homophobic vagrant named The Bishop (Reg E. Cathey) that terrorizes the block.  The problem I've had with other movies by this director is how they all seem "improvised" on the spot ... and yet he's not very good at making things feel "natural" in any way, and the jarring shift in third act which involves a violent encounter (and the disposal of a body) goes against the film school whimsy of what preceded it.  It might have helped to further develop the Polly character to explain her motivation in "helping out" to such an extent: has she no romantic life of her own?  Or is she merely an angelic womb?