These kinds of situations are sticky. If you want to do them as displayed you could do as you suggested: 3-5 displayed to narrative text. If you are transcribing displayed to the itemized material the columns would have to start in cell 7 because the itemized subdivisions are 3-5. The columns themselves require a blank line before and after as you stated in your post.
I want to suggest another format -- which is just a suggestion. If you consider the data to be runover to the material that precedes it, you could start the columns in the cell where the runovers to the material begin. I have attached a document showing both ways. I would welcome comments from readers and experts as to the legitimacy of this interpretation.
In the simbraille, runover on braille pages 1-2; displayed on braille pages 3-4.