Guy who developed the ICE adapter here, Bandwidth of 8 Mbit/s should be fine. I don't have the exact bandwidth requirements in mind, but I remember sth like 20KB/s per player.
It's not just the download that matters, but especially the upload. About the traffic, Client and ICE overhead is insignificant, it's 95% compressed game data.
Back when testing ICE, we had a player with 1 Mbit/s download and they weren't able to play anything 8+. So for dual gap I'd say 4+ Mbit/s will be fine. Beware though that the game is peer to peer and therefore traffic symmetrical, you will need the same thing for uplink as well. (Have been playing 16 player games with 2 Mbit/s up for ages).
About latency, that's a different story. You've come at an unlucky time. The FAF server is currently misconfigured, causing the latency estimation to Faforever.com to fail.
ICE tries to establish a direct connection, but uses a fallback in case that might not be possible (due to e. g. a symmetric NAT as it might be the case in a hotel environment).
We've got a relay server in australia specifically for oceanian players, but due to the mentioned current issue, your ICE adapter will not detect that that should be used.
So it relays your traffic via the server in Nuremeberg, for a round trip from player A->B->A, that means A->Europe->B->Europe->A. So you're going 4 times around half the world. That's the reason your in game latency is currently that high.
We're working on a fix. In the mean time, I've also added a workaround into the ice adapter which uses some fallback servers for the latency estimation (not the relaying, just the figuring out of "should I use the oceanian relay").
You can find the new adapter here: https://github.com/FAForever/java-ice-adapter/releases/tag/v3.1.0
I'm trying to get it inro the release candidate soon, you can test it by replacing the faf-ice-adapter.jar in the natives folder in the install dir of the client.
This will cause your adapter to correctly detect that faforever.com is too far away and use the correct relay. If you're lucky, your relay candidate will be used. It might be the case though for some players in your team, that are in oceania too and still run the old adapter, that their, european relay candidate is used, so you may end up with the same issue, till a fix is released to everyone. (although the issue won't be on your side then)
You can also send me an adapter log after testing, then I can take a look which candidates (relay/direct/...) and which relay were chosen.
If you have any other questions / need help / ideas troubleshooting network issues, feel free to message me on Discord (Official FAF server).