Oh wow, such a lenghty lore dive ♥ Thanks for taking interest in my game!!
The timeline is more like this:
+ The land was unusable for a long time after some unspecified military conflict
+ Then people took interest in this place and the city of Huta-Grobno was formed
As for the location you're right, it's placed in again, some unspecified place in central / eastern Europe. In general it's set in similar but somewhat alternative world with a slightly different timeline,technology and of course, a layer of supernatural stuff hehe
It makes me so happy to know that you read the additional booklet!!