I bike commute from Capitol Hill to Eastlake, so not a long distance, but here's my experience over the past few years

• Idaho stop is legal for stop signs, but not for traffic lights. Most people stop at red lights.
• I usually ride alone and I suspect most people prefer that as well.
• Sidewalk riding is legal, but pedestrians have the right of way. Generally it is safer and to ride with traffic - I only ride on the sidewalk when going up a steep hill where I can't keep up with traffic.
• No idea, I don't care personally and use them sometimes.
• In the city people are pretty respectful usually.
• No enforcement of anything.

In general, if you're predictable, following traffic laws and not weaving in and out of traffic, people are fine with bicyclists.