Thank for everyone's interest in my situation. You have all given me such great advise!
the baskets are a lot stronger than they look. I think they are made from rattan or bamboo and then cured with some sort of stain. They are very tough. When they get older they get more brittle, but its very difficult - if not impossible - to break the new ones. They are also heavy. I put a rock over the large hole at the very top to add more weight. When I am not using them I can stack them one top of each other.
We get different predators here. Last year my ducks were picked off one a week from the pond outside my house. Then I found a huge snake skin. Next week I saw the python on the bank a few inches away from the sleeping ducks! I had to re home the last few ducks. One of my friends chickens was bitten by a cobra, and I have see a few around my house. I also get mongoose in the garden, but they don't seem interested in the chickens. Street dogs can be a big problem for any hens that fly out of the garden. But if a particular dog gets a reputation for killing chickens then someone usually poisons it. There are many poor families here living nearly a subsistence life, so their animals are very valuable to them.
The biggest threat is to the chicks. We have a large bird that looks like a cross between a crow and a pheasant. Its black with red eyes and a long tail and orange wings. It will smash and eat any eggs it can and also kill and eat the chicks and ducklings if it gets the chance. My dog was good at keeping them away.
As for my dog.........She is acting normally again. As long and the chickens are in the run she is not interested. Phew. I had ideas she was going to try to dig in under the fence. I will never let them free range when the dog is out. I now even shut the dog in the house when I go out to be safe. (although I hate the idea of her being bored indoors).
She was crazy the day of the attack and when she tried to bite me she was not playing. It was like she reverted to a wild animal - like a fox. I think she was just so wound up with the excitement. She growled and showed all her teeth and tried to bite my hand, but I was quick and she just scratched my skin. I am sure its not seizures and she has been spayed. The hen will make it, but she has lots a lot of her top hen confidence now.
Thanks again everyone!