If, while flying an aeroplane at very high altitude, a window or door breaks away, is the pressure differential enough to suck a human human out?

yes. especially if they are very near the breach..
it's called explosive decompression..
after cabin pressure has normalized the danger of being sucked out becomes much less..

Yes, absolutely. Technically you'd be blown out (rather than sucked out) because it'd be the rapidly evacuating air that blows you out with it.

I don't think the pressure differential is so great that it will suck an adult sized human out. Small things may get sucked out. Wind blast or broken seats may fly away with the air speed. But that's my view with all the respect for the view you have expressed

Yes, here's proof
http://www.smh.com.au/world/explosion-forces-plane-to-make-emergency-landing-in-somalia-20160202-gmkav3.html

If nearby, sure. Ever watch the thing on the plane that gives you the outside temp and the altitude. It doesn't show pressure, but it's way less up there so huge wind out the hole when it first breaks open.

I would never fly that particular airline again if that happened to me. Just saying. 🤔

I was once sucked out a window at low altitude, it was a bus station washroom window in Oldham...