23:26:12.518: Output 'adv_file_output': Number of skipped frames due to encoding lag: 1 (0.0%)
Your CPU is near limit
Your log shows you are recording and streaming at a time. I´m not sure, but I think this requires more CPU. This would explain being near limit.
I would disable preview while streaming and recording.
1920x1080x30FPS: raise to 3500 KBps to get better image.
BUT with 2500 you get this:
23:26:10.957: Output 'adv_stream': Number of dropped frames due to insufficient bandwidth/connection stalls: 177 (0.1%)
If you raise bitrate you probably get network issues.
You can try Twitch Test and check if there is an alternative server with quality above 80
http://www.teamliquid.net/forum/tech-support/478845-twitchtest-twitch-bandwidth-tester
Use TCP Window 64 K and 60 sec