Which will be your main router - this TD-W8980 or another device?
Could you give more details, please?
Enter failsafe mode, then do the factory reset. This will wipe all your configuration changes and put the device back into working condition. Of course you can also try to fix the broken config manually.
To enable the VLAN tagging on xDSL, replace dsl0 with dsl0.836 in the network configuration.
I need to connect my modem into brigde mode and connect to my RJ11 cable I will then obtain the internal mac address my ISP use to authenticate me on their network from my computer using wireshark, the dslam will send the mac in the packets header
As I understand it, the bridge mode is just needed temporarily in order to extract the MAC address from the DSL traffic, then you can return to a router configuration.
Edit the LAN interface, go to Physical settings, and add dsl0 or dsl0.836 to the bridge interfaces.
Another option could be to install tcpdump on the OpenWrt router and run tcpdump -n -e -i dsl0. This works without bridge mode and wireshark.