1) use the slider in the logitech dpi settings dont use the profiles. U can manually delete them and just have one. Use whatever dpi u like.
2) Sensitivity is personal, lower the sense on the xim app to your taste
3)Its preference. But most keep it on. U have AA with the controller too, u will become used to it. Its called target compensation in the in game settings if u want to switch it off.
4)There are many threads and videos on this. Check youtube ximgameplay for example.
5)its how it should be. Remember ur left stick is keyboard. Ur right is mouse. Ur using a converter not a native mouse and keyboard. U can however change it with xim, it explains in that video above.
6) Keep it simple. You dont need any advanced settings etc. Get some experience first. Oh and practice makes perfect.