Use a faster preset until...
18:35:32: Total frames encoded: 12272, total frames duplicated: 2032 (16.56%)
18:35:32: Number of frames skipped due to encoder lag: 1204 (9.81%)
... the percent of duped and skipped frames are less than 1%.
And yeah don't stream 1080p60. Even if you can encode and send it, it'll stutter on playback, unfortunately. For troublefree playback, limit your stream to 1080p30 or 720p60. This isn't something that you can "get to work" with a better computer or better settings, its a fundamental problem with this sort of video streaming.