Bungalow expansion to single-family house - costs, KfW funding & planning

Yes, that's what I meant, when mentioning the 300000 you mentioned

For a single-family house new build, we would budget just under €300,000 for the house. In addition, there would be land, ancillary costs, connections, garage, garden, kitchen, walls, floors, etc.
The price would include expansion of the attic, underfloor heating, decentralized ventilation, shutters, 2 mansard gables, and KfW 55 standard. The house would have approx. 180-190m². All without a basement.

That's not €1600/sqm.

Yes, that's what I meant, when mentioning the 300000 you mentioned. That is not 1600 euros/sqm.

Including finished attic. But my main concern here is the bungalow renovation.

The more you renovate, the more the costs approach those of a new build. If I understand correctly, you want to more or less gut renovate the ground floor and add another story. Not much of the original substance will be preserved (basically, I only see the ground floor walls, but maybe that’s misleading), so you won’t end up much cheaper than a new build as you think.

Who with experience can give me approximate prices for the following work/materials?

Detailed information is very unlikely to be given here. Prices vary quite a bit regionally, and even if someone still remembers their heating prices from two years ago, they do not necessarily apply to your house.
This is also not a craftsmen forum...

Everything is not necessarily cheaper than a new build. Renovating an existing house is worthwhile if you can contribute a large part of your own physical effort and construction knowledge, a new build is not approved as the existing property, or the renovation is worth it as a labor of love.
Otherwise, in my opinion, you hardly save anything given the effort or size of the conversion/renovation as you plan it.
I would also ask a professional and not just laypeople like us.

Secondary escape routes are escape routes in the event of fire when the stairwell is no longer available due to smoke.

Second escape routes are escape routes in case of fire when the stairwell is no longer accessible due to smoke.

Are they required from x m2? I have never seen them in a single-family house.