Hi Looker, all joined now ;)
Welcome :)
To be sure about your father's Polish citizenship the application must be filled and submitted to the embassy. It is also crucial for your efforts to obtain Polish citizenship.
The form is very detailed, but the more meaningful informations will be noted the better for the whole case. Another issue that it must be filled in Polish.
Do you think its unwise to write that these details about my father are unknown on my application (in the father's memoir part)?
Everything you put on this document must be true, if you are not certain about something it may be better just write unknown with (if possible) a short note.
Good luck!