First off, v5 is deprecated but it still works perfectly fine, and will continue to work as there is currently no planned removal date. It was v3 that was removed and because your request there is using v3 it’s not working.
Secondly, your broadcaster id is your user ID, you can use the Get Users endpoint to see what your user id is: https://dev.twitch.tv/docs/api/reference#get-users
Finally, to get an OAuth token with the correct scope you’ll need to go through the Authentication process, specify the scope you wish to ask permission for, and then go through that auth flow to be granted a token that you can use. Details for the auth process can be found here: https://dev.twitch.tv/docs/authentication/getting-tokens-oauth