I am using the Motorola SB5101 SURFboard Cable Modem that Metrocast sent us back in 2009ish when we signed up for the internet service.
That is your problem. I would start by getting a DOCSIS3 modem.
You will only hit 35mb on that modem if no one else is on the Internet at all. With DOCSIS3, it will bond more channels to allow you to get the higher speeds. -- Dream as if you'll live forever, live as if you'll die today.
Disclaimer: These are MY comments, my employer cant be held responsible.