Most of your questions can be asked by browsing around or searching by keyword. That having been said, I will answer with what my experiences are with my ducks (Muscovy's) and chickens.
1-Breeds you like I think depend on what your "backyard" is like. I didn't want alot of noise, and I live in a country area, so I wanted ducks that were large and hearty. I chose Muscovys and they are a great fit.
2-I have used turkey starter grower to raise all my ducks. This has gotten expensive, so I have switched to unmedicated chick starter. The ducks are doing fine. I also make sure they get plenty of greens and I add niacin to their food.
3-You can put them in a water bath a few inches deep at days old, but always supervised. Mine don't get a pool until completely feathered.
4-I have raised them with chicks. When you first put them together, just monitor them to make sure no one is picking on anyone. Ducks, chicks or anything else can start picking on a weak one.
5-Pool for Muscovys is different from others because they don't "like" the water as much as other ducks. Kiddie pool is fine for Muscovys. Answers about the other breeds I'll leave to others. Mine have a 3X5 2' deep pond. Pools or ponds will need to be filtered or cleaned. Again there are many ways to set this up, so I would cruize around BYC a bit before making your decision.
Welcome to the wonderful world of Ducks!
