Complex paths won't convert to shape = Pathfinder Exclude tool not preserving 'cutouts' properly :'(

Hi, all!

I have been ripping my hair out about this for a week now, contacting Adobe support and searching online for hours to no avail, so any help would be MUCH appreciated! 

I am simply trying to subtract the artwork in the foreground (white) from the background (black). So essential if they were one layer, everything in white would be transparent.

I drew the background myself in Illustrator, but used brushes to create the white artwork, also in Illustrator:

All I want to do is cut the white details out of the black silhouette. However, when I use the Exclude or Minus Front via Pathfinder, it loses a lot of the detail like so:

I've tried expanding the white detail but that does nothing. I've tried converting it to a shape but keep getting the same error message: "1698 of 1709 objects not converted." So clearly it's a very complex design. Outline Stroke doesn't do anything either.

I've tried using the Shape Builder tool but it was literally taking something over an hour to delete a single teeny tiny white shape, and was still losing detail in the end.

I'm at a total loss! This is for a really rad food cooperative trying to make healthy, local food more accessible within the community, especially for underserved groups.  I'm happy to share the ai file should someone want to try their hand at it themselves. Thank you in advance for any and all help!