Dear @Great Man,
Yes, the information is correct about the time being reduced to 6 years. It is not just for Duldung holders, as a person with 25,5 you can also receive this permit.
For people with the permit 25b Absatz 1, family reunification for their husband/wife and minor children is possible. Here is more information (via an online translation) about family reunification with this permit (it first talks about 25b Abs. 6 and 25b Abs. 4 but then there is information about 25b Abs. 1 which you would be entitled to):
I hope that helps, let us know if you have any other questions.