In no particular order, these are the things I can think to experiment with or question:
Have you tried not using the "Dangerous Configuration" options check box and the "Advanced Linklayer Options"? The defaults sometimes work best.
What type of ISP service do you have? Setting Per Packet Overhead too high shouldn't be too much of a problem, but you could set it lower if you have cable modem service for example.
Are you gaming off a WiFi AP, or connected by wired Ethernet to your R4S? The problem could be your WiFi interface if your on an AP.
Finally, have you tried lowering ingress and egress rates a bit more to see if that improves things?