2. Is an external step required for the roof escape route?

The proper contact would probably have been the building authority.

I don't think so. They only inspect. But they don't assess the execution.

We are talking about an escape route and not a fire escape.

As far as I know, there is no fire escape in private single-family houses.
Make sure you get out safely.
I have experienced myself how burned-out houses look or how the path from the ground floor to the attic has burned down. Then you're glad if you can get out from somewhere.
You don't wait for the fire department there either – you have to get out of the house.

Thank you both for the feedback. The requirements regarding the window (for RLP) we fulfill, but regarding "weitergehende Vorrichtungen" we do not make any progress. I am still unsure how to accomplish that (and also see the risk with further requirements for living space - what would those actually look like?).

Does the attic have more rooms? There must be a first and second escape route per floor, not per room!