Behold this guide is specifically meant for low speed (<1 Mbit/s), plus it has some minor flaws which has been pointed out in the comments above. I would at least encourage you to look at these guides (too):
General XSplit configuration/settings Q&A (the biggest on TL):
Good alternate 3rd party capture driver for better performance (less lag input):
I strongly encourage people not to blindly trust the result of Speedtest.net. It is only a rough estimate on the bandwidth to whatever server you choose, but it will never be the actual streaming server at Twitch.tv - and it will very unlikely reflect whatever ingestion Twitch.tv may or may not have (I have a hunch that ~80-90% are using the same server - because they have never changed their default settings). Therefore, use the far more precise measurement feature (the "Test Bandwidth" button) that Twitch.tv just have built into their XSplit plugin.