Aperion audio has a quick guide here;
that will help you get going. I personally prefer a MC Audio set up with the surrounds back 100-100 degrees and at ear level, some might not agree, but this is what works for me.
Now, as for #3, YES and the difference can be HUGE depending on the speaker. If you want it to look really discrete, have you considered going with in walls? Many companies are producing very high quality in walls now a days that are specifically designed for this so they don't need the room to breath many normal speakers do to sound best.