Doesn't the ONT device run an OS similar to a router? (Mine is running RouterOS) It has 2 ports (LAN side and WAN side which is the Optical Fibre). The WAN Side is the one that gets a Public IP and then the LAN side is then configured with a static IP on the same subnet as the WAN side of the...
I guess it's better late than never. This is 2 years later. You seem to have 2 routers (1 small one where the Fibre terminates and the bigger one where your devices connect to) from what I understand and you need to port forward both routers as explained by this article...