On filling large data

As soon as the form will exist I will of course share it here.
For the moment different forms are achieving some of your need but not yet one only form does it all (but it will soon).
here a first one using select with map appearance and hiding already selected grid cells :

Here a showcase about "auto" updating csv file (will soon be obsolete with entity based data collection)

And finally here an example where we pull a static value form csv file to show it in a note (lines 65 to 78) of the xlsform :