1) The "Three Valentines" Questions:
- What's the episode where Niles is pressing his trousers and sets fire to Frasier's apartment?
- What's the episode where Niles faints at the sight of blood?
- What's the episode where Niles sets his trousers on fire?
- What's the episode which has a bit which is near silent, and is the funniest 7 minutes of 'Frasier' I saw?
The answer to all these questions is the same episode: Episode 6.14 - Three Valentines
If you're still not sure, here's a pic from the episode:

2) What is the music playing in Episode 8.03 - The Great Crane Robbery, while Frasier tries out new flat layouts?
It's "Classical Gas" by Mason Williams

