Hello, Elle!
It will all be fine tomorrow!
Now, this puzzle was created for an American crossword puzzle convention.
It seems to have an American tone to it.
5D is "Bu sbo y", "buy" is purchase, around first letters of "should be ordered".
I presume busboy is a waiter's assistant!
24 tied me in knots!
"Durum" is a type of wheat, often used for pasta.
Wheat have ears, part of an ear is a "drum", with the second letter of m"u"sic.
I think that was very tough!
Nanograms looks good, but the dear Lord only knows what the parse is!
My suggestion is that the answer is based on the word "kissogram", meaning the "nans/grannies" are older kissograms.
But, that is only my opinion, and may be a bit iffy!