Gigablast has been an upgrade nightmare

This past weekend, my girlfriend and I had enough of our spotty internet coverage. So I chatted in with a couple of service reps and they both said the same thing. Our modem, which was a Motorola SB6183, was causing packet loss errors. After talking it over with the rep, we decided to up our speed to Gigablast and upgrade our modem to a DOCSIS 3.1 modem. We originally had the 150mb/sec plan and with 2 Xbox’s and a gaming PC, the additional speed would greatly help us out. We go out, buy a Netgear CMS1000v2, put our less than 4 month old Netgear 7960p behind it and get everything set up. Now our internet speed is absolutely terrible.  We would get 150 with our old connection and it would slow to less than 100 on/off.  With the new modem, we barely see 80mb/s and usually closer to 50mb/s. I have done the hard reset of all of my equipment, including resetting the wireless router to original factory settings. Nothing has worked. I have contacted three different service reps through the chat and they all tell me it’s my equipment. It’s clearly not my equipment.  Low and behold I search the forums here, and find the exact same problem I am having. 

https://forums.cox.com/forum_home/internet_forum/f/internet-forum/22600/looks-like-things-are-bad-again-gigablast-speedtest-330-35

This is the exact same problem I am having except with even slower speeds than this person in the above link.  I have tried to tell the service chat, the problem is with the line into the house, and they have all told me its my equipment.  My equipment was working perfectly before updating the service plan and the modem. I have tested different coax locations in the house with the same results. This has been extremely frustrating and to add insult to injury I get an email from Cox stating I am over my data limit for the month. I am posting here to see if I can get this fixed ASAP.......