1. Forget about getting all scientific on the dish. Locate peak signal and that is that. Standing there saying "but the settings are exactly what ... says" does not get you signal.
2. One of the great mysteries of life
3. Yes. The recommended limit is 75' but many of us here are running far longer runs than that. I have one going roughly 90' to a
DiSEqC switch and then another 55' or so to the lnbf (circular
C Band). There are some here saying they are in the 200' range. Personal experience has shown me that the longer run does mess with the DiSEqC switch a bit.
4. If so it is nothing noticable.
5. In general no.
Without stating your location and what sat and tp you are looking at I could not say if that was a respectable number to be getting on your strength and quality.