As successful solvers found, the first parenthetical number referred to the number of letters to "MIX" (from the end of the relevant grid entries, as clued in 64D), and the second parenthetical number referred to the number of letters of a grid entry where the "Mixed" word would also serve as a suitable answer (the "MATCH"). Both the Mix initial letter and the Match initial letter were required to form the answer, as hinted in 2D (Arrange EIGHT words . . .).
I thought this would play easier, but after comments from a number of solvers I can see that the number of anagrams of STAL and SNAP provided some difficulty. I had in mind that there are only two anagrams of LEM (ELM and MEL), and with BLANC in the grid, that would provide the AHA moment to the metanism.
Anyway, thanks to everyone who toiled to the end. It's a great forum and everyone is totally supportive, even when undeserving!