Packet Loss on a New XB8-T +install

I signed up for 800 mbps service last week and the tech came out to install the modem. Even though they are seeing 800+, when I do a speed test on a PC as the only connection to the modem, I get speeds of 360 max. I am using PingPlotter to look for packet loss and I'm seeing tons of it. AT the modem and at various hops along the way. Here's a typical report.

When I call the Xfinity "help" line, the support people don't know what Packet Loss is. Their solutions are for me to upgrade my service, or to just go away. I've been having buffering and glitches with all streaming services, even podcasts for several weeks. My initial contact about this was last week and his solution was to upgrade my service, so here I am, a week later with the same issue. How do I get this fixed? Mike