The number of viewers does not matter for you, it matters for twitch and their servers only, as they have to distribute it to the viewers. You only stream a single stream with 2mbit to them. Youtube Music will mainly use your download speed, only CS-GO and Team Speak will use the upload of your connection and they both should not use too much.
You probably use much less than 3mbit of your upload while doing all the stuff at the same time.
FaHu is certainly right, higher streaming bitrates are only interesting for Youtube or if you are a twitch partner and get transcodes. But even then, 3500kbit is the unofficial maximum on twitch, so you will still have enough upload in that case. You will only need a higher upload if you plan to stream to youtube at higher bitrates.