Reading Aloud – Should ‘And’ Be Added Before the Last Number?

In your example:

Notice that these examples fall under well-established categories of acceptable, standard English.

Think of a hierarchal chart with categories and sub-categories. In your example, "these examples" are sub-categories of "well-established categories", as far as I understand the context.

In such a chart, sub-categories are below categories, so fall under is correct.

In your second examples:

Voters fall into three main categories.
Students over 25 fall into a different category.

Here, the voters (or students) are part of (inside) the mentioned category. Therefore, fall into is correct.

To tell and to say are very flexible in their usage. A rule of thumb: when you tell something, you are giving particular information, and when you say something, you are letting your opinion be known or sharing your thoughts.

These are all idiomatic:

Psssst! ... I have a secret to tell you!

Angry mother to disobedient teenage daughter:

Come downstairs this instant, young lady! I have something to say to you!

The locution Bartleby uses is somewhat archaic today. Bartleby is saying that he does not want to have anything to do with the person. He does not want to find himself in a situation where the two of them are conversing about anything.