next gen speed configuration - CM3000 and RAX70

Hi, 

Next Gen Speed Tier is available in my area and I got a modem off this list that works for that. 

I had an xfinity tech visit and he can pull 1800MB download and ~400MB upload directly off of the coax cable. 

However, I max out at 900 down / 300 up. I have the most expensive xfinity plan (e.g. theoretically 2gig down). 

When I log into my modem (Nighthawk CM3000) this is what I see: 

When I log into router (Nighthawk Tri-Ban AX8 RAX70) this is what I see: 

I tried changing the settings in the modem to enable port aggregation but the only thing that after the modem rebooted is kick me off the xfinity system. 

I then had to chat with xfinity support to get them to reconnect me - but I couldn't get them to do that with the next gen speeds allowed. 

I do not want to rent an xfinity system. I have too many IoT devices and need to be able to manage my own network. 

Does anyone know how to set this up so that I can achieve the speeds that should be possible here? 

Thank you