Having a functional stream on twitch will be based on your computer specs and upload speed of your internet plan. You have two major types of encoding available including x264 and NVENC. The former places more stress on your CPU and the GPU for the latter. It depends on your internet connection but its been quoted that you require about 10% more upload speed than the maximum bitrate you're capable of using to stream. If the upload speed on your plan says 3.0 Mbps then you should be able to safely stream at 2000-2500 bitrate but with Shaw 300 and 15.0 Mbps you can easily cap out at the twitch maximum of 6000 bitrate. My connection's stability took a hit since the new year and we are seeing many posts on the forums complaining about unstable livestreaming on twitch. This is most likely on Shaw's end and you are helpless until they get it fixed. Internet 600 would do nothing to improve your stream.