Fascinating. The fact some songs are based on KOF'98 which was released in mid 1998 makes the Hummer port way more recent than one would think. Final Fight 3 was seemingly manufactured around September 1998. KoF'96 containing the unused string LET'S HIT THE STREETS in its code suggests it was build atop (partly) Final Fight 3, or at least a work in progress version. It's also the closing title of the NT-6xxx line which contains more than a hundread of different entries. All from 1997 and 1998. Thus it was likely released at the very end of 1998.
It should be released before Final Fight 3, as FF3 was their last game released by JY. Due to the release of ‘98 it was released sometime late July or (more likely) August 1998. Maybe you used an early reprint for reference?
I don't know how to explain this, but I have some sort of synasthaesia for music and time, and it's definitely telling me this was released in the summer of 1998.
So to sum it up in one post:
Boss Team stage - These Dreams by Jim Croce
Fatal Fury Team stage - New York's Not My Home by Jim Croce
Japan Team stage - Unknown
Iori Team stage - KOF '98 Art of Fighting team theme
(which itself is Todoh's theme from AoF 2, but it's obvious where they got it from)
Goenitz stage - Still unknown, but now that I think of it it sounds very strongly like the bridge from Fairy, which was Chizuru's theme in 96. Compare from 1:20:
https://m.youtube.com/watch?v=lseEsjtm1MsUnused tracks:
Esaka (possibly the 98 version?)
KoF ‘98 - In Spite of One’s Age
Unknown, possibly Rhythmic Hallucination.
Street Fighter Zero 2 ending theme (left over from SFZ297)