Ans 1. For the side surround speakers should be between 90 and 110 degrees to your seating and about 2.5 to 3 feet above your ear height for the best performance. The Back surround speakers should be spaced 3-4 feet between eachother and should be ofcourse behind you or in celing if you dont have a close space.. or do not want to place on stands behind your seating area.
Ans 2. Probably the first answer did cover that one.
Ans 3. Monoprice speaker cable is great...order in bulk so as incase you run out.
Ans 4. Checkout Emotiva speaker package, http://emotiva.com/shop/cart.php?m=product_detail&p=26, ofcourse you would have to find a reciever that would be able to handle 4 ohm speakers, but a good reciever should be able to handle them real good. This are great speakers and there is a 30 day in home trial...best place to try out speakers is in home as your setup. They have excellent deals on amplifiers as well. http://emotiva.com/shop/cart.php?m=product_detail&p=32 add that to your speaker package and you have a system and then you dont need a great reciever and the good thing is you would never have to worry about the system power running low.. with this speaker and amp you would only have to have a reciever with pre-outs and you would be in heaven...