Hello

-The alignment should already be accurate...First set up roughly, when a picture has been found, adjust to a maximum using the signal strength by finely changing the direction and inclination.
-It doesn't matter whether you use a large or small dish, as long as it is a satellite receiver.
- Every cable has a certain loss which attenuates the signal, the longer the cable, the greater the loss. if the cable is infinitely long, there will eventually be nothing at the front! How many is a few metres........ In the normal case it is enough.
Hope I could help.
Greetings