We tend to wear rose colored glasses about what happened before, if you had exact stats from that time, you'd find they aren't as great as you remember. We fed ours similarly, nobody lived past 4, or layed past 3. We thought it was normal.
Roosters shouldn't have layer feed, she's correct but...
That's why you're not getting eggs.
Scratch is not good for chickens, it's a treat, it's not supposed to be fed everyday. You only feed it once or twice a week and less than a tablespoon per bird.
Scratch is high in fat and carbs, fed in excess, it causes laying issues, vitamin deficiency and...
If the rooster is mean, get rid of him or make him soup. He's a liability and chicken keeping is so much more peaceful without dealing with a turd. Your hens don't need him and aggression is often a genetic trait.
Valbazen goat wormer is what most people use, you dose it individually...
Unfortunately, she could be carring incurable viruses. It's best to get rid of her quickly. If you weren't so attached, I recommend cull and burn. Be sure to sanitize that coop.