How is dharma formed? I believe that the word 'dharma' (among other things) refers to the constituent elements of a body and mind, and that the Buddhist should find those dharmas void of a person, and perhaps any substantial quality whatsoever.

How is dharma formed?

"Form" is one of the skandhas, what a body-and-mind (I believe 'nama-rupa' in the sanskrit word for that?) has contact with in order to generate the rest of us.

Is there a Buddhist philosopher who talks or debates, perhaps at length, and ideally grounded in sutras, about how dharmas depend upon form?

I suspect there's a major / basic teaching on this, just wanted to make sure I'm not missing anything, when i research this question, which I find interesting because the contemporary world seems to make its ideas out of "form".
I guess you are asking about Dependent Origination?

You can find detailed information in "Learning materials for Dependent Origination (Paṭiccasamuppāda) in Theravada Buddhism".

For a perspective from the Abhidhamma, "The Abhidhamma in Practice" may be helpful.