Please use
www.speedtest.net to see how your upload is.
Your download and upload are somewhat unrelated and your upload will usually be considerably slower than your download. An upload of about 1-2 mb/s should be enough to stream 360p quality streams or even 480p. You could upload higher quality video with an upload rate of 1-2 mb/s but it may cause stuttering, if you use twitch however they design it to cause as little stuttering as possible, instead the video buffers silently and then releases the full video when it's done buffering with an artificial delay. This WILL probably mean that people watching your stream are 10-20 seconds behind you but it will also mean there won't be too much stuttering.
A download of 12 mb/s is more than enough to download netflix, depending on the quality. Worst case scenario, just start loading the video and have a break, let the video load while you do something else and when it is fully, or partially loaded, then watch it. Download or upload speeds won't affect whether you can or can't download stuff.
Your bandwidth should be enough to handle two internet connections, but if it isn't you may should just do what Echoes says or stream (or download) lower quality videos.