as for my internet, my isp will be coming this Friday to set up my upgrade I order which is 60 Down and 30 Up, and I'll be using OBS to broadcast. The set up I have now will be my computer for this year and most of next year.
Just try it, you got nothing to loose. Stream your gameplay to twitch and let a friend check, if the frames are smooth, if not, try to cut down on background tasks like a web-browser. Also dont use XSplit, try OBS, its waaay less power-hungry. 720p at a low framerate should be possible, but no fancy overlays and stuff. If you want clear answers read up on the twitch.tv support forums. Trust me, someone there has the same specs and knows what is possible. Your Internet-Speed is fine BTW.