Hey guys how would you finish the hardwood around these stairs (pictures below)?

My plan is to:

Run bullnosing along the stair edge and the edge of the wall facing the stairs. Over the top of the stair stringers I plan to miter the bullnosing at 45, come out over top of the stringer, and then miter again to get back to the edge of the wall. Hopefully the picture below will help explain what I mean.

On the other side of the bullnosing I plan to miter the hardwood boards that butt up against the nosing, use my router to cut a groove and use a reversing spline between the boards and the nosing.

I have two concerns though:

1) The miter cuts need to be exact to look flush against the bullnosing. Who knows if the stairs are perfectly square to the rest of the room, or if the hardwood is still at a perfect 45. So what's the best way to get these cuts perfect? Just trial and error?

2) The miter cuts of the bullnosing itself might chip up the edges, which would be visible. Any recommendations to get a finer cut? Better blade? Cut the board face down?



And my plan for the bullnosing:

 

There's more than one way to do it, and others will chime in with possibly better methods. Here's mine. I would buy two extra staircase treads. Rip them down to 3 1/2" leaving the bullnose. Turn the piece on it's side and rip off the excess 2 3/4" deep, leaving 3/4" of finished wood. Then lay it back down and rip off the excess leaving 3/4" piece that will match up to your flooring and a 1 1/4" bullnose, which is substantial and needed at the overlay. I also cut a groove in the back edge to accept the flooring tongue or transition strip. The reason I do this is because I don't like the cheezy ones made of MDF and I can match the finish, grain, etc.
Gosh, I can do this in a minute and a half, but explaining it is taking an hour. I'll try to draw something up so you will have a visual and post it back later.
Try this: