Cat friends' sudden hostility towards each other
We have two cats, a 6-year-old male and a 4-year-old female, both neutered. They have been the best friends, the most sweet and loving cats there can be.
We have had them for about a year, and got them from a home where they have been together as well. We never had any trouble before this.
About a week ago, the male got his paw stuck somewhere while playing, freaked out and started trashing about. From this, the female flipped out and attacked the male with tooth and claw.
We separated them and they were both still quite freaked out for the whole day. The next day, we tried letting them in the same room, and the female attacked the male right away.
Since then we've been trying to re-introduce them slowly, letting them smell each other and feeding them near the closed door, and then see each other through a screen door, switching territories every now and then, the whole works.
The male has been a bit wary still. The female would like to go nearer, but doesn't seem at all aggressive. She has tried going through the screen door, but she is very curious in nature.
They still seemed relaxed even while the other one was near the screen door, ate and played with us. They are very interested in each other though, and definitely concentrate on each other, stare and so on. But all seemed cool.
So we let them in the same room, to test it out, trying to keep them occupied with toys and treats and letting the male come there on his own, chasing a toy.
It was in the female's "territory", not the male's safe room. The female ran towards the male, he hissed and ran away and the female bolted after him, yelling and knocking over everything in its path.
They both calm down fast once they're separated again, so it's not quite as bad as in the beginning. Should we still take it slower, keeping the screen door between them? Is this a territorial battle that they need to just have at some point? What's the best way to go here?