No not every table has a view and even tables with a view can be blocked if people are standing outside in front of the window. You can always go out on the dock to watch.
As the PP said, not all tables have a view of the fireworks, but many do. We had a table in the inner row on the first level and could see just fine. We were there in December during a cold spell so no one was out on the veranda, but I gather that can be a problem for those that remain at their table when the weather is better.
Yes, the pipe in the music and dim the lights inside the resturant.
One time we were able to watch from our table. Usually people stand in on the porch and block all the views from the table. Our waiter waited to bring out desserts so we could go out and watch the fireworks.
Narcoossee's is a must do for us and have been there four times during the fireworks. I will agree, that people can block your view when standing out on the balcony but it is really not that big of a deal to get up and watch yourself from the deck. The staff is very accommodating knowing that you are booking your adr around this time and will coordinate your meal around the fireworks if you let them know.
We've watched the fireworks from Narcoossee's several times. Each time we were just finishing dinner when the music started and we went out onto the boat dock. We never planned it that way, it just worked out that way.