Those two statements contradict each other…
I hardly stream, but when I do, it uses at least 8Mbps.
Also, you said you get a lag spike and then it crashes? Are you monitoring your GPU with anything like MSI afterburner? This sounds a lot like when I would get lag spikes with DX12, which would cause the game to crash. Try running the game in DX11.
Also, you said you have smaller network packets enabled? Make sure you have the mod “Player list plus” uninstalled. If you have that mod with smaller network packets enabled, it causes all kinds of lag, disconnects, and other random things.