A General Licensee will always have a 4 letter call sign.
About the dedicated line to the modem... I mean from the demarc (location on the side of the house) to the cable modem is what I am talking about.
I only have one thing on my cable modem cable... err the cable modem.
IOW, you have a "cable TV" side and a "Cable Modem" side from the de-marc.
Run all your TVs from one side and you cable modem only on the other side.
When I said use the existing to pull two, I meant pull two cables through to your TV area. Allowing for you have to a dedicated Cable Modem Cable and a Cable TV cable there.
It is upto you. But I heartily suggest a second cable from teh demarc to your cable modem.