I don't have personal experience with guardian dogs, but I have read enough about them to have answers to some of the most common questions.
They DO require training and supervision, especially at first. It's pretty common for the guardian dog to kill some chickens (or other livestock) when it's a playful puppy, and when it's a "teenager" testing things out. This does not happen with every such dog, but it shows up fairly often in questions and discussions. I don't know all the details, but at a minimum they need to learn that playing with the livestock is not permitted. They are commonly considered to need two years to mature, which is a long time to be supervising a puppy!
If you don't have time to work regularly on training the dog you already have that is a problem, you probably don't have enough time to raise & supervise a guardian dog either. Buying an adult would save you the two years of puppy raising, but you would still need to devote quite a bit of time to getting it settled in, and supervising it for a while as it learns what the rules are at your place.
If you get a guardian breed as a puppy, it will certainly not protect the poultry from your other dogs while it is a puppy. It might protect them after it grows up, but it might not. That will probably be affected by whether it considers the other dog dominant to it, and by whether the other dog teaches the guardian that chicken-chasing is fun. Also, what kind of "protect" would you want it to do? It might bark or growl, but the older dog might ignore that and kill chickens anyway. Would you want the guardian dog to kill or injure the older dog? That is a real possibility in some situations.
For breed, one that is available to you, where the parents are already guarding poultry, would probably be the best choice. Each breed has some dogs that would work for your purpose, and some that would not. So getting a dog that already does the job would be great except that such dogs are usually not for sale. Getting a puppy from parents who are doing the job is often possible, and gives a good chance of getting a puppy with the right background to work well if you raise & train it right.
I don't know about the temperature. But if you find someone local with guardian dogs, you can ask them about their dogs and the heat.
Given what you've described, I think you would be happier with better fences instead of trying to get a guardian dog. But that's just my guess, and I may be completely wrong.
. I keep asking if he has seen yoke running down their mouths and he has not. They go inside the coop while chickens are free ranging and he blames them - I dunno. Do dogs like to eat eggs? And what about the shell, none been found laying around. I think it's just that each chicken does not lay each and every day is all.
