Very slow Internet Download Speeds even after Xfinity repairs in my area

I received abrand new RG6 coax cable today.  I replaced the existing coax cable running to the cable modem with this new one.  The speed test results were in line with previous results and very poor. I then moved the cable modem to the basement where the cable feed comes into the building.  There was a splitter connecting to a cable going into the wall with a spare port open.  I connected to that port. 

The speed test results were the similar to previous poor results.  Here are two runs using the Ookla Speedtest app using the set up in the basement:

https://www.speedtest.net/my-result/d/40e10466-758d-4d05-b41f-51085293c74f

https://www.speedtest.net/my-result/d/f3df538d-d119-4d05-a7c6-9f050fccb75a

The equipment used in the basement is:

• New RG6 coax cable
• Surface Laptop (with USB 3.0)
• CAT 5e Ethernet cable
• Anker 1000 MB USB Ethernet Dongle
• Netgear CM1000

The Surface was plugged directly into the cable modem (no router).

I've used this equipment before (minus the new coax) and have gotten much, much faster results.

Combined with the fact that my neighbor ran a speed test for me yesterday and he got his provisioned speed for 600 Mbps using his Xfinity XB6 (I think it was that; it was definitely an XB devices), it tells me that the issue is unlikely related to the wiring in my building.  I've seen issues where Comcast pushes a new configuration file to modems or updates the CMTS configuration, causing compatibility issues with cable modems, usually 3rd party ones.