-2 bytes thanks to Emigna.

-2 bytes thanks to Emigna (Significant refactor, thanks man).

05AB1E, 25 24 22 bytes

A7£œ9ôvyJðý"."«})9ô9£»

Try it online!

A7£                     # Push first 7 letters of the alphabet.
   œ                    # All 5040 permutations of "abcdefg".
    9ô                  # Split into pieces of 9 (Sentences).
       vy       }       # For each piece...
         Jðý"."«        # Join by spaces and finish with a period.
                 )9ô    # Split into pieces of 9 (paragraphs).
                    9£  # Take only the first 9 paragraphs.
                      » # Join by newlines and implicitly print.

05AB1E, 25 24 22 20 bytes

-2 bytes thanks to Emigna.

A7£œJðý72ô€¨'.«9ô9£»

Try it online!

A7£                     # Push first 7 letters of the alphabet.
   œJðý                 # All 5040 permutations of "abcdefg" joined by spaces.
       72ô              # Split into pieces of 72 (Sentences).
          €             # For each piece...
           ¨'.«         # Lop of the last char and concat a period.
               9ô       # Split into pieces of 9 (paragraphs).
                 9£     # Take only the first 9 paragraphs.
                   »    # Join by newlines and implicitly print.

Turns out 810 word version is shorter than 729 version.

Turns out the 810 word version is shorter than the 729 word version.