Did you update the server? I had much lagg with 3 or more friends on my Linux server that was running at 30% resources. (20% CPU and 25%RAM i5-8G)

Since I updated this weekend, the server uses 37%RAM and the same CPU, all runs alot better. Almost fine I can say!

Send and receive limits are kind of an old thing, I never touched this and everyone have 100Kb+ up/down. Also, there is no P2P when using dedicated server setup, this is server<>client.

Update the server.