Stair top riser - hollow floors and angled wall tops

[LowMill]

I am (new to) using HD Architectural and having a few problems with stairs in a split level house.

 

Prob 1) The riser from the top stair is not carpeted like all the other risers and the top newel is missing.

 

Prob 2) I have created 'Open Below' rooms for the stairwell which works fine but the camera views look straight into the floorspace - how can I blank-off the wall space?

The attached pic shows both problems.

 

Prob 3) I want to have a partition wall where the top is angled to match in with the stairs above but cannot find a way to angle the top of the wall.

 

Hope someone can help.

Thanks 

Clive