$ perl -lwe '$/ = \128; ++$hist[tr/\0//c] while <>; print "$_: $hist[$
+_]" for 0..$#hist;' lookzpM.byte-*
0: 12003438
1: 148200
2: 147874
...
42: 330481
43: 33028
[download]

This means you have plenty of room to pack the lines as: {N} ({i}{x})* {pad}.
Compute q8 = (i ^ m7) & 127; q9 = (x ^ HASH_LEN);

Average 15.984 elements per line. Lots of looping and branches can be avoided this way.

Update. One more thing occurs to me. Indeed, those files compress rather well: lzma packs them 1:2500!