If the house is that old I would expect the cable modem to be run directly not interface with the likely oldet cable TV/Antrnna wires.

I was a cable guy coming to install cable at your home I wouldn't want to trust your existing wires I would just want to run a new wire right to one spot.

And simple and one point of failure equals vastly less chance for a call back and as an installer of anything that's what I'm all about!