Hyphenation

Here's a paragraph I'm working on, in which all numbers are to be written out. I'm confused about the rule on hyphenation when it comes to quantity and as modifiers. Can anyone help?

The troublesome paragraph:

"...the numbers are staggering: in the mid-nineteenth century, over seventy-five thousand acres of rice were productive in the region, yielding one-hundred-and-sixty million pounds of rice. In 1860, when the total national crop of rice was five million bushels, three-and-a-half million of them were grown in a narrow stretch of land near the South Carolina coast. By 1901, however, only thirty-five-thousand acres were being planted.

I've gone back and forth between inserting and removing the hyphen between "five" and "thousand" and "sixty" and "million".

Paul