A mirror is a great idea!
Sound advice, but I do want to say that pairs CAN do well together...not always, and in certain situations ↓
I have several aviaries with pairs of coturnix, they do great together and actually form a strong pair bond. They will go broody if I let them. BUT this is in an aviary setting...smallest is 4ft x 6ft with plants and plenty of hiding places.
I've noticed behaviour has a lot to do with the environment they are kept in.
I don't think they would behave like they are had I put two new birds in a small quail cage without cover.
My quail housed in wire cages off the ground are MUCH more aggressive breeders! Like you said, 1 male to a minimum of 3 hens to be safe.