Don’t think I’ve been getting the error 400, as that pertains to Client ID not being included - have you checked your code to ensure you are always sending a Client ID with your API call?
Sometimes I’ll get a 404 but that’s not very often.
As for checking the stream on whether its live or not, the endpoint is:
https://api.twitch.tv/kraken/streams/highstakespoke
The stream object will be null if the stream is offline - it will contain data if it is live.