The first thing that seems odd is that DD7's P-MAP reports from last year always gave Lexile scores as a range and not a single number. The Lexile range from P-MAP can go at least up to 729-879 so it doesn't look like a ceiling issue.
NWEA's assessment scores and the associated reports and resources provided are extremely useful tools for informing instruction in the classroom, but they should not be used in exclusion to other data sources. Using triangulation assures that the most informed and appropriate decisions are being made in behalf of each student.
Since you have 2 pieces of data showing a higher reading level (DRA score and what he chooses to read) and MAP showing a lower level, I'd advocate for making sure higher level books are available for him to choose at school.
