Your speed test looks o/k. Which speed tier are you actually subscribed to ?
Is that the only server / site that is slow or is it a more general issue ?
Perhaps that particular server(s) is / are congested / busy, or perhaps there is a routing issue to it ?
It’s Microsoft. My comcast speed locally is fine. I have no alternate location for downloads. I typically get 10Mbps downloads from MS. I hope this just not a very poor peering arrangement with MS, or the signs of the loss of Net Newtrality going into effect.
You could run a traceroute to the server to possibly locate the bottleneck. I don't believe that Comcast peers directly with MS. There are typically third party backbone / transit providers involved in the routing.