Sorry to be so picky and wish I could be more helpful. Section 7b on page 37 is preceded by Section 7a (no parentheses) which has several instances of (b) under it. On page 37 is Section 7b(no parens) THEN under (2) is (b) in parens. A number or letter with or without parentheses is critical in this numbering scheme and one of the many reasons why it is often difficult to follow. Without the page number I could not tell which instance of (b) you were referrring to. I couldn't tell which subsection it is under.
See page 1 of your braille, lines 15, 19, 21. I don't know what those page numbers are. Is that Nemeth with continuation letters? I don't know this notation but I could not find the corresponding item in the print. That's why I concluded that the print and braille were not matching. I could not find entry text that matched the braille in my attempt to decipher the page number.
The rule says what it says about centering Unit and Part Headings. The one example in Formats without unit and part headings does not show chapters centered.
If you used 1-5,3-7, you could show the chapter (cont.) in 1-5 with no page number and the next subsection that starts that vollume in 3-7 with its page number.
Just my suggestion. This is not an easy problem.
I do have a feeling that the new guidelines will make this sort of things easier. For one thing, there won't be any continuation letters in contents!