Translation:František lived in a pretty strange house then.
"Dost" tedy znamená "pretty" or "much", že?
It can mean 'pretty' as in quite... or 'enough' or 'much', yes.
'Really' is not a good option for 'dost' in this case?
The word order "Frantisek then lived in a pretty strange house" is perfectly correct in English and should not be marked incorrect.