I see that a 4.18.20-100.fc27 is already in koji, and unfortunately 4.18.xx is now EOL. May I suggest that f27 to get a new 4.18.20 build with the STIBP backport reverted please? (Current 4.19.3-rc reverts that already.)
Works OK for me on my x86_64 setup.
Patch for #1249364 is not included in this build.
Downloaded libmad-0.15.1b-26.el6.i686.rpm and libmad-devel-0.15.1b-26.el6.i686.rpm, ran rpm -Fvh libmad*rpm, seems to work on my centos-6.10 setup.
Although I suggest flipping the order of patches 6 and 7 in the spec file to avoid offsets when patching.