OBS stats look good, but you have some settings that don't play well with Twitch:
04:53:01: Video Encoding: x264
04:53:01: fps: 30
04:53:01: width: 852, height: 480
04:53:01: preset: veryfast
04:53:01: profile: high
04:53:01: keyint: 250
04:53:01: CBR: yes
04:53:01: CFR: yes
04:53:01: max bitrate: 3500
04:53:01: buffer size: 3500
04:53:01: ------------------------------------------
04:53:03: Using RTMP service: Twitch
04:53:03: Server selection: rtmp://live-jfk.twitch.tv/app
04:53:03: Interface: Realtek PCIe GBE Family Controller (ethernet, 1000 mbps)
04:53:03: Completed handshake with rtmp://live-jfk.twitch.tv/app in 179 ms.
04:53:04: SO_SNDBUF was at 65536
04:53:13: Trying to hook process: RocketLeague.exe
04:53:20: using memory capture
04:54:18: GraphicsCaptureSource::NewCapture: eliminating old capture
04:54:18: using memory capture
04:58:29: Total frames encoded: 9799, total frames duplicated: 17 (0.17%)
04:58:29: Total frames rendered: 9818, number of late frames: 3 (0.03%) (it's okay for some frames to be late)
You should set the Key Interval (keyint) to 2 seconds (i.e. 60 frames). You have it set to 250 frames, which Twitch doesn't like. Also considering you're sending at 852x480, you should set the bitrate lower. Set it to 2000 bitrate and buffer at most, but you can get away with even lower than that, like 1500 or even 1000.
The total frames duplicated is only 0.17%, which is excellent. OBS is running fine, I wouldn't worry about the preview window. If your preview window is actually from Twitch, then you shouldn't watch your stream from the same IP you're sending it from, that causes problems. But I assume you meant the OBS preview window.