Interjection from my husband, who doesn't have an account here but reads a lot:
Have the infrared heating calculated by the energy consultant to see if it is even possible with KfW40. How do you get it for half the price if it is offered for more expensive? Who installs it?
Also, the south-facing window areas play a significant role in the calculation – those are very small and narrow in your case... Due to the roof overhang, it could also get quite dark on the south side of the upper floor.
Keyword: domestic hot water heat pump:
With infrared heating, you have radiant heat and convert electricity into heat 1:1 – that is already not very efficient. If you then also use a domestic hot water heat pump, which usually converts ambient heat into hot water, I see dark times for the limits for funding. Those are something entirely different from just achieving KfW40 and are constantly being adjusted or tightened.
From the beginning, before you plan technically further, I would bring an energy consultant on board so you don’t have to overturn everything again later.