Bufferbloat to the max with 1.2gbps down and 35mbps up - XB8-T

I am extremely desperate right now-- this is a cry for help 😭. Xfinity says they're not doing any network improvements and nothing is down in my area. I think it's easier to show the types of 'spikes' in latency I see through my internet connection:

I'd love to seek any help possible from any strangers that are out there that could help. Here's the things I've tried:

• Restarting gateway tons of times
• I had a tech out here run a few speed tests through the modem and he said the 'speed is fine' and that 'nothing was wrong with the Xfinity connectivity' based on the signals. I think he was purely operating for down and up speeds.
• Confirmed that I experience this through a laptop (wireless) and desktop PC (wired) directly connected through a gateway. Both environments receive D/F grades.
  • Also tried cat 5e, 6, 7, 8 cables. Still nothing to help buffering issues.
• Tried tweaking different configs via https://www.speedguide.net/articles/windows-1011-tcp-ip-tweaks-5077 . Nothing is helping.
• All DNS testing resulted in higher latency times (per the screenshot) via https://dnsspeedtest.online/. Busy times (8PM) or non-busy times (2AM) testing yielded no difference.

The DNS testing and the laptop/desktop testing really tells me there's a single point of failure somewhere, I just don't know where. I'm truly at a loss and can no longer bear the issue. My family still loves our connection because they can still stream 🤦. Is there anything else I can test or try to improve my bufferbloat?