Layer feed is usually 16%. You can use an all flock, grower, or starter/grower in the 18 -20% range (that's what I feed) and just make sure you have oyster shell available all the time for calcium in another feeder so they can take what they need, those other feeds don't have the extra calcium. None of those foods in the bowl are 'bad', it just means she eats that instead of her feed. There are a lot of trace minerals and nutrients that they need which are very hard to get in otherwise. I agree with you on the scratch, that should be only occasionally. It's generally very high carb and can make them fat, which leads to other health problems.
It's a good rule of thumb to limit treats, and treats means anything other than feed, to 10% or less of the total diet. It is very, very easy to over do them, we are probably all guilty of it at one time or another. On average, a laying hen will eat 1/4 lb of food a day (obviously that is an average and things will vary based on size, activity level, etc), that's only 4 ounces. So treats would be limited to 0.4 ounces, that's not very much at all.
