Arris SB8200 Dropping Signal 5-10 times an hour

I am paying for 700 Mbps internet service and the cable modem is a new Arris SB8200.  The modem drops the signal five-ten times an hour and the internet has become pretty much useless here.  I have had technicians at the property, a lot of COAX re-wiring, spent hours and hours on the phone with Comcast.  Went to a Xfinity store, read hundreds of posts, called Arris and nobody can fix this problem.  The modem signal power downstream is around 10 dBmV per channel.  Upstream is in consistently 33 dBmV.  This is apparently way out of specification according to the modem manufacturer but Comcast keeps telling me it's fine.  It's obviously not fine.  I am paying ridiculous money for this service and have 4 people doing home school and the signal drops non-stop.  All PC's are gigabit ethernet hard wired.  No wi-fi connections.  I have requested Comcast call backs and they never call.  I need a solution to this.  The latest insult is that starting today they are limiting data to 1.2 TB per month.  Somehow, with our extremely faulty internet their website says we used 378 GB today January 1 (literally in 15 hours).  There is obviously something very wrong.  Can anyone fix this??