Thanks a lot for making it easy to help by providing data and concrete examples :-).
You can use:
One Row To Many to duplicate rows as per your Month + 1 column
The new row key holds a numeric suffix starting with 1 to distinguish each of the duplicated rows. You can extract that so you know by how many month you need to shift your Start Date forward
use either Column Expressions (legacy) if you are on a version before 5.5 or
use Expression nodes to manipulate the date by first shifting start date forward by the number of months extracted from the row key and then shifting that result backward by one day
