Can I get it to just pick a point instead of going through an entire document?
Yes. If you want to use Draftsmith specifically at certain places rather than the whole thing, for example, if you want suggestions for a particular sentence, click your cursor to the start of the sentence or section, and Draftsmith with jump to that help you edit there.
Also, within a specific paragraph, Draftsmith will split out the text sentence-by-sentence, allowing you to make changes to one specific sentence, and leave all others unchanged.
To ensure a sentence is left unchanged, click the purple tab on the right to switch back to the original text.