Baunebenkosten calculation realistic?

Much has already been said. What I still notice:
Dirt rainwater with 3000 could be tight, depending on the length of the pipe.
Paving work with 6000 could be tight, depending on the size of the paving. But with a 500m² property it could work.

Have you checked whether they build the attic usable in the construction service description? So do you at least get a sealed folding ladder upwards, is a railing installed upstairs, are there floorboards or anything else so that you can put something down there?
I once read that the cheap providers like to save on that.

They will not only save on that.

I would have reservations too, but as far as I understand, the choice of the construction company is already made.

@danifx With house number the application for a house number is meant