I don't have this router, so I cannot tell. And I could not find some reference configuration in the forum for your router.
Safe choice is to reset to defaults and start over, unless someone else can guide you.
The above is from an Archer V2, so it will likely not be the same for your router. But the point I want to make is that you don't need to configure VLAN 7 between your router and the modem, because the Vigor is already taking care of it on its WAN port (by default anyway).
Other than as @trendy said, this looks correct to send tagged packets to the modem. Having both CPU ports receiving packets from VLAN 7 isn't going to break anything, but you should turn VLAN 7 off on eth1.
You can easily switch between tagged and untagged to the modem by changing the setting on the WAN port in the switch. You don't have to change the VLAN number back to 2.
Examine the log file to see if any pppoe negotiation is occurring.
The Vigor modem takes care of the vlan tag towards the provider. The OpenWrt router does not have to use a VLAN tag on its WAN port. If @PlanetDyna removes the VLAN tagging from OpenWrt WAN port it should work. It works like this for me.
@PlanetDyna when you log into the Vigor and go to Internet Access -> General Setup you see both ADSL and VDSL2 enabled with VLAN tag 7 and prio 0? If you go to PPPoE/PPPoA you see the client mode disabled? This is the default.
On OpenWrt in switch config your screenshots show tagged with vlan 7 on WAN port. Mine shows untagged and works like that.
I think it's weird that you have both both CPU (eth0) and CPU (eth1) showing up as tagged for both your VLANs. Looking at https://openwrt.org/toh/linksys/linksys_wrt1900acs I think it should be CPU (eth0) tagged 7 (and off for 1) and CPU (eth1) tagged 1 (and off for 7).