Since the wan physical port is now in a bridge, it can't also be accessed directly by the pppoe driver with the option device wan which is still configured there.
Create another bridge-vlan inside br-iptv for the router Internet wan traffic. It can have any vlan number (other than 103 of course)-- I suggest 2 as that is conventional for wans. It should be untagged on the wan port, which is connected to the modem. Then change the device of the wan (and wan6, if you are using IPv6 that way) interface(s) to br-iptv.2.