Two things:
1. "She stated that unfortunately they had two techs leave late the previous week unexpectedly and that he was looking to hire multiple people."
Multiple people don't leave a company unexpectedly. Something is fucked up big time there.
2. Both sides agreed on a interview at 3 p.m. and that's it. He should treat you with the same amount of respect as you do. Even if he has to reschedule the interview to 3:05 p.m., he should talk to you. It's on his/their part to let you know.
Honestly, you don't want to work there, even for short time while looking for another job. I did this many times before and I don't regret anything. If people don't respect you, fuck them. I don't care how busy there are and nobody should put up with shit like this. Stuff like this turns into so much stress and makes people sick to the bone which eventually can lead to cancer. Don't listen to the people to suck it up, because you shouldn't. There will a better job opportunity come along with people that actually respect you as a person and your time.