Xfinity Support; Bridge Mode/Admin Tool/Xb8

So I recently ran into issues with my WiFi setup when moving. My setup consisted of a Xb7 in Bridge mode to allow my use of an External Router. If I remember correctly I also had firewall issues so I had the Xb7 firewall/security disabled and then relied on my router's really good firewall. I did this all via the Admin Tool @ "10.0.0.1".

The 2nd to last time I moved I had zero problems. All I did was unplug devices from the wall and plug them back in at the new location, and everything worked seamlessly. I lived there for 2 years and never needed the Admin tool the whole time I was there. 
This time, I was prompted to reactivate my gateway after turning everything on at my current location. So I did, and then I wasn't getting Internet from my personal Router anymore. This is my issue that I haven't been able to solve.

I have factory reset my device a few dozen times on my own and even with customer support on the phone and my credentials are not resetting to the default "admin"/"password".
I did hear from a customer support agent and someone on this forum that for models XB6 and above, 10.0.0.1 is disabled. This makes more sense to me since I haven't been able to login to the Admin tool with the password my Password Manager remembers, or with the Default "admin"/"password".
The last customer support agent I spoke to was someone that my issue was escalated to, and they told me that "the Admin tool should still be accessible and that the Admin tool credentials were tied to the device", to paraphrase. Maybe there's been some misunderstanding of the information floating around, but after receiving a Xb8 in the mail and activating it.. the issue with the Admin tool not accepting even the default "admin"/"password" has now persisted between devices.

Unfortunately 2 of the customer support agents I spoke with had no luck remotely setting my device into Bridge mode either.

I have many devices, and a smart home system that all rely on the connectivity that my router provides me with and a lot of port-forwarding and other settings are still on my router so I would really rather get this issue solved instead of giving up. There have also been a few smart home devices that can't get internet via my gateway anymore, while the only device that has had a consistent connection has been a single desktop computer. A bit disappointing.

I'm open to any suggestions whether or not they come from xfinity staff or not.

NOTE:

To Factory Reset the gateway I have been holding the WPS button on the back for 60 secs as there is no longer a small reset button. I have also power cycled the device with a short off period and an extended period left unplugged for at least 10mins to see if a longer cycle made any difference.

I'm aware of the 3 different kinds of credentials:

• the UserID and password for Xfinity websites and apps
• the SSID and password you use to connect a device to Wifi
• the gateway admin tool login ID and password