The biggest risk to the aircraft was probably if it had hit the horizontal stabilizer. Someone at NTSB will probably estimate the departure speed based on the pressures and aerodynamics to see how close that was.

I don't know that the outcome would have been all that different if it had been at cruise vs. 14K feet. The O2 system is sized to allow the pilots time to get the plane down to 10K well before it runs out, and the pressure difference from inside to outside wouldn't be all that different from what it was when the plug departed. I was actually surprised at how high the internal pressure still was at 14K feet. It would have taken a few minutes longer for them to get the plane back onto the ground in PDX.

ETA: the main increase in risk at cruise would probably be more people with their seatbelts unbuckled and possibly in the aisle.