Submitted corrections to internal for approval ~month ago and awaiting response. Feeling impatient/stressed with hardbound deadline imminent.... anyone else been in a similar situation/got advice? What happens if I don't hear back in time for the deadline?

Unfortunately there's no way to tell- it took me several months. Depends on your internal's circumstances. Follow-up with him every 3 weeks or so is my suggestion. I've been there and know how frustrating it can be. If you don't hear back in time it's ok you'll just graduated officially later than what you had in mind. I ended up graduating 2 months after when I had hoped to graduate. In the great scheme of things tbh, it's not a big deal.