I am reading this thread very surprised ... specific hobby ... why not have a separate room for it in a two-person household and get it out of the house technology etc.? Sauna .. would be worth considering putting it on the ground floor near the other bathroom. Then you can also use the cool air outside in winter.
Much else has already been said ... door position kitchen restricts kitchen planning from the outset.
Then the wood-burning stove catches the eye, the chimney is not planned for in the upper floor ... and, as a rule, such a chimney on the outer wall of a house with a hipped roof looks rather strange.
If I understand your symmetry obsession correctly, then all 4 sides are supposed to look as identical as possible? If you just enter city villa as a search term in Google and click on images, this is almost never the case, not all are floor-to-ceiling windows. In the bathroom, for example, this leads to the washbasin being planned in a dark corner without lateral natural light incidence etc.
You write a lot .. yes, you can get used to that, or it is better than now etc. But, you want to spend over 300,000 euros, you don’t want to just get used to it or have it only a little better than now, but you want as much as possible the personal optimum. How many living sqm does the purchase contract you signed actually include? According to the floor plan, it is about 140 sqm?
If you have already signed the notarized purchase contract for the plot, you do not need to fear that someone will snatch the plot away from you, even if the transfer in the land register has not yet been made.
Very important would be building boundaries or building lines (if there are any) and approximate measurements of the plot because the garage still has to be placed somewhere, and for room planning it would also be useful to know the possibilities of the plot.