Don't consider myself a cat expert, but have had dogs my entire 63 years of life and cats for the last 10 years.
Some say cat are stupid. I say no they are not just creatures of routine. My cats get fed in the morning when we wake up, around 4pm and again around 8 pm. DST screws them. They have been at the feeding room door an hour ahead meowing. If we sleep in, they are on top of us, saying, "It is feed time."
My cats get fed in a separate room. Could you establish a separate feeding room for the cats?
I would put the dog feed up and start feeding the dog and cat at the time in separate rooms. The dog will learn very fast that it is feeding time and the cats also.
My cats will eat the dog's left over feed at times and it hasn't hurt the. You are correct that cat food is not good for dogs, especially one that small. Higher fat content cat food.
Elderly mom. My mom is 91 and I understand. I am wondering if you can get her one of those elderly pick-em up devices and maybe take a hair dryer or heat gun to bend the handle of a measuring cup to make it easy for her to feed them without bending over.
My cats aren't spoilt, Just well loved.