Plot Points

I know, I know...one should not analyze the plot of this kind of movie too closely but still...

Why Kelsey didn't reveal the secret staircase earlier makes no sense. It's not like they could make it go away.

So...the whole town thought the uncle went into a jealous rage, stabbed his wife, played the organ with bloody fingers, then killed himself by jumping out of the window.

But the reality was that the nephew stabbed his aunt and then pushed his uncle out of the window. Right? Okay, so who played the organ with bloody fingers? Do we presume that the killer nephew did this? When? After pitching his uncle out of the window with a notable thud? Before? Hmm. And all those fingerprints. I suppose he had gloves on.

When Kelsey staged all that crazy stuff including stabbing the painting, why did he go to the trouble of replacing the painting to make Luther look crazy?