Also your OBS is outdated 21.1.0, but I don't think it would change the network issue you are having. Update it just in case, if running the update inside OBS(Help > Check For Updates) doesn't work then manually download and install it:
https://obsproject.com/download
Try other twitch servers, do this first though do this part on the link he provided:
"
TWITCH.TV USERS: You can use
TwitchTest to find the server that you have the best bandwidth to, and the max bit rate you can stream to that server at. For the best results, set Duration to Medium and uncheck any regions you're not in. After the test runs, look for the server with the highest quality rating. If two or more are tied, use the one with the most bitrate. Note that a quality score of at least 80 is the general baseline for a stable stream. "
So according to that test then try all the best different servers you can use. If on all of them you are still having the same issue then you will need to contact your ISP(Internet Service Provider) and complain to them that you can't live stream on Twitch, connection way too unstable and the supposed "upload speed" is BS, that they need to help you out.
Do post the screenshot of that TwitchTest so we can see how it went for you
