Dog is a Picky Eater?
I also have a Chihuahua, I do give him fruits and vegetables, which he loves. I also have a dog dish which is always full of his dog food which he does eat. I have noticed that he tends to eat in the evening.
Flies Biting Dogs Ears?
What about adding vinegar to your dogs water, not much, so he will still drink it. Maybe this will help with the flies on dogs.