Please post a logfile from a live streaming session (not just an offline test). There's a sticky at the top of the forum detailing how to do this.
3300kbps is pretty massive overkill for 720p, even at
60fps. For 720@30, you should be just fine at 1500-2000, and the Twitch servers will be much happier with you, as will your SO's downstream connection. Twitch recommends sticking under 2000kbps at this point (their ingest servers are being a bit overloaded lately). As an example, I run 720@60 on 2500-2700kbps with excellent quality. But I still have a LOT of my viewers report choppy playback on the Source stream.
Also, run a 6MB test at
http://testmy.net/upload to confirm your
constant throughput; this is what matters for livestreaming, and speedtest doesn't check that, just overall averaged dead-file transfer rate. Many ISPs will give you an effective rating, but provide a very 'bursty' connection which runs at a drastically lower constant rate, then SPIKES far above the rated speed in short bursts. Dead files (non-streamed) can take advantage of these bursts. Live streams cannot.
Dropped frames = connection issue, or remote server issue. (Displayed bottom-right on OBS)
Lagged/delayed frames = local system issue. (Check your logfile for these!)
Choppy playback =/= lagged or dropped frames. (At least not all the time)