My kitten is suddenly terrified of my dog?

Let me first give you a bit of background here - about 8 months ago we got a puppy, and already had 2 adult female cats. The puppy is an American Akita cross Rottweiler. This puppy is now 10 months old, but 2 months ago we were asked to rescue a male tabby that had been found abandoned during the floods we were having. We took him in, on the condition we'd see how he got on with ours.

Well, him and the girls were in a slight war to find their places in the hierarchy, but they were getting on well. Now him and the puppy - despite the major size difference - were best friends. They slept together, played together, chased each other - were rarely apart, except when eating. See, my puppy is good as gold in all aspects with humans - but other animals, when it comes to food, he can show agression. Usually, it's just a warning, though he has got into fights with my partner's mothers dog. However, these are both intact males (he will be castrated when he turns a year old) and we felt a lot of the aggression was down to that, and my dog not having to ever share his food with another dog.

Yesterday morning, everything was as usual when myself and my partner went food shopping. We were gone about two hours, and when we came back, found that dog had managed to get a box of his treats out the cupboard, destroyed the packaging and then ate them all. He was in trouble and had an upset stomach. But where was the kitten?

We found him - our crazy, energetic, loopy kitten that's normally chasing everyone, attacking anything that moves - was hidden behind the sofa. Whenever we tried to get near, he ran in panic. When we eventually got hold of him, we checked him over. There were no wounds, no reactions as if in pain - he's running and jumping fine - but he was trembling and seemed in a complete panic mode with huge pupils, darting his head here there and everywhere, and the fur on his head and neck was slobbered all over and crusty dried. We shut him out of the front room separate from the dog, concerned that he had gone to investigate what the dog had snuck out, and maybe got snapped at and shook?

But health wise - he is 100%. We took him into out bedroom last night (he's not normally allowed) and when it was just myself and my partner, no other animals, he quickly became himself again, chasing feet under the duvet and jumping all over me.

However, this morning it was the same again - the second he saw the dog, he went crazy and hid behind the kitchen units. He's only just come out now, and he's glued to my side hiding as the dog is outside but he's still wary.

As his general health is fine and it seems to just be fear, what would you suggest to help him get comfy with his best friend again? Our dog is very confused as to why he's suddenly been shut away from the cats, and doesn't seem to understand why our kitten won't play. Any advice on how to get him confident again would be much appreciated. We were thinking of just separating them when we aren't in, just in case, but when we're in leaving him to it and letting the kitten come out with the dog around in his own time? But I'm concerned that the stress and the hiding won't be good for him.