Run your cable to the RF in on TV to tune cable channels. Run antenna to the DTV converter box, feed the DTV converter box to TV with A/V cables (yellow,red and white)
Do it right the first time run cable to where you need it and the same with sat. do not mix the two and you will not have any problems.
As for hooking cable to a sat box, that is stupid. anyone feeding sat to TV with RF should be shot.
Use A/V or S cable
My point is before you install a dish, look at how and if you can get a NEW run of RG-6 from dish to location of Sat rec.
If that is not possible tell the customer why and how you will try some substandard way of doing it
Save your money and use the free dish that comes with the DSS system. Your C band dish has a F/D of .3 to .4 and the little dish is .6 to .7 and offset. The big dish will not work much better than the small one.