Is the act of suffocating itself considered to be taking damage?
After 10 minutes, the Hag should be out of air due to the properties of the Portable Hole. At that point she would be suffocating, but not taking any “damage” until after her third turn (she has a Con mod of +3). At the start of her 4th turn in the Portable Hole, she would immediately drop to 0 hit points and be dying.
Would the poison's effect immediately wear off as soon as she starts suffocating? Or would she stay unconscious until she started dying?