1: I personally believe God (or a God, not necessarily what the common example of God is) exists, simply because we have emotions. While I understand there is a scientific explanation for emotions, I don't see what scientific purpose they serve. Me feeling jealous because someone has a faster car than me does not help the human race survive, for example.
1(a): I don't believe God can be proven nor disproven, scientifically or logically.
2: God wanted to something to do, something to exist, and our universe was intelligently created, but with plenty of room and resources for humans (or possibly other intelligent life on other planets) to expand on their own. Life just seems to work too well, and there seems like there have been an awful lot of coincidences in the path that humans have had over the last millions of years to get to where we are today.
2(a): I don't believe there's a sound basis though. It's all too much for anyone to grasp or understand, scientifically or religiously. There are HUGE logic flaws and gaps in either case, I think.
3: I believe it is because God created the universe, but did not give it restraints. God allowed his creations to do as they please. Evil, as we think of it, is only natural. Similarly, is there much fun in keeping a puppy in a cage for it's entire life?