I'd recommend setting your bitrate higher than 2500. Your max alloted bitrate is between 5000 and 6000 so do a speedtest to see which works best for you for 1080p streaming. In fact, I'd also recommend changing the Output Scale Resolution to 720p. Then your preset should be set to "very fast". I know 1080p should be doable on your pc, but I have no experience with World of Tanks and this game could possibly have high cpu utilization.
Not sure why these are different for you, but your advanced settings should be on default, Color Format NV12, YUV color 601, YUV Range Partial.