In fact, the current draft is based on the initial draft by the architect. We have then more or less strongly modified it. The architect is a friend of ours and does this sort of on the side.
Before I kick this architect out, it would be more appropriate to compare your modifications with his planning. Usually, the layman makes everything worse with his "improvements".
... is it worth adapting this?
What does adapting mean? Moving a wall by 30cm is not enough here.
The question that now arises for me is: Should we discard the entire floor plan,
You have to!
500k€ excl. outdoor facilities with a high share of own labor.
So including incidental construction costs?! ... that won't work even with a lot of own labor. Strike out the garage and basement and possibly another 20sqm of living space, then it might work. So 160sqm x €3000 …. €480,000 Incidental construction costs €50,000 Minus own labor €30,000 Then you get to €500,000!