Unfortunately I feel Airbnb will support this guest. The leaking pipe would cause an issue for many guests . Also constant moving is not ideal - I would personally wish to cancel in such circumstances.
We can all face the nightmare of maintainence emergencies and you seemed to genuinely want to resolve, offer another apartment etc. All reflects well on you. But we must put ourselves in the guests shoes also.
If possible take this as huge learning curve. Maybe keep the number of a few tradespeople on your phone who could fix an issue immediately.
I would speak with Airbnb direct. Discuss and they will likely cancel reservation with no penalties to you and refund the guest . You should not cancel via the auto system as all kinds of problems will commence. Good luck.