Regarding your question, I'd say it's a bit tight. Last time I get a ED in Penang, there were people getting Tourist and Business visas just in 5 minutes, but me and another girl, both for ED, had to wait almost two hours... I think nobody can tell you, you could be out in a minute or in one hour.
Then, it's a bit more than 30 minutes because it's rush hour and the main avenue and then the road could be crowded.
You can do it, but it all depends on the time they take in the Consulate...
You can extend in advance, but how long in advance depends on the office - in Chiang Mai you can extend 45 days in advance, but others only allow one week in advance.
The extension is added to your current "permission of stay" date you you can extend in advance and you will not "lose" days.
Be aware that in addition to all your prepared paperwork, in that consulate is mandatory a copy of your entry stamp into Malaysia - usually there is a van parked just in front of the consulate with printers/copiers to get any copy/photo you'd need last minute.
It could be that the applicant couldn't prove he/she actually studied - failing to pass the interview.
But just for information, the Language Institute in CMU is not part of the University; it's a separate Institute, with its own rules etc. Almost as a private school auspicied by CMU.
And when I asked there, I did not feel very confident about the quality as a proper school for ED visa, as the schedule was just 2 days a week and some free weeks every 2 months...