If you don't want to manually fix a lot of things, I think you will at minimum need some formulas. Below is one possible option:
Create delimiters with new formula column
Concat Items(Words(:Letter Sequence, ""), " ")
Then use text to columns with the new delimiter character
Stack the data table with the new columns
Create new formula column to get the correct Start Letter numbers
Col Min(:Start Letter No., :Letter Sequence) + Col Cumulative Sum(1, :Letter Sequence)
Copy that just created column to other column to get End Letter No (or use formula)
Then you need one more formula, to change first letter's Delta D to 0
If(Row() == Col Min(Row(), :Letter Sequence),
0,
:Delta D
)
Finally cleanup column names to match what you want
-Jarmo