In reality you don't have a "pair", you have a male and a female. There is no pair bonding, and there is no parental care. The males goal in life is to spawn, he builds a nest and trys to attract willing females. Once a willing female has gone down into his nest and spawns with him, she swims away and broods her fry over a rocky habitat far away from the male and it is likelytheyl'll never have contact again. In our tanks there is no place for the female to retreat, you don't have any other females for him to try to attract. They may have even actually spawned, but he wanted to spawn again and again, and this type of harassment could make her swallow the brood, or he could have even knocked it out of her mouth. If she was not willing at all, it doesn't matter, he just kept trying until he ultilmately trashed her.
They breed best in harem type groups where you have 6 - 8 females to one male, where it is harder for one fish to get singled out. Providing dither fish might help, but these guys are just so big and aggressive that they probably wouldn't even notice them. Same problem with trying do them in a community type set up. Although not impossible, to breed one on one, it is extremely hard as you have experienced.
You may want to nurse her back to health one more time, divide the tank so they can see each other, and then after a few weeks take out the divider but don't remove your eyes from them. If they don't spawn in a few hours, or if he starts to trash her, then you are there, to put the divider back in immediatley.
The condiiton of your female is going to a critical factor of whether she is going to spawn or not. You want her in prime condition, which means you need to feed her some live foods. Black worms, earthworms, guppies or culls would be good. You need her to be feeling her best, or nothing is going to happen. Like most males <grin> he will be ready at a moments notice!
It is a gorgeous fish, and I totally relate to your desire to spawn them, but it is a tough one, especially one on one in an aquarium.