Yamaha FG375S , looking for top desk color.

Have you glued the crack itself?  How wide is it?  I normally humidify a guitar before attempting to fix a crack.  Many times it will come back together and can be cleated & glued with thin superglue.  Glue won't fill an open crack well and will look like crap..

OUCH!!  A failed previous repair.  I'd try dabbing on some shellac.  It'll add color, but maybe the exact color, and it'll seal the wood.  A few coats, let it dry for a few days, scrape, sand & polish.

I have no idea.  You'd have to experiment with samples of the spruce you used.  Matching colors is an art.

Not a chance.  Who knows if they recorded any of that detail, and they probably didn't share it.  And Japanese translates extremely poorly to English.  I've read the symbols can mean different things, depending on the subject.  So the translations can be very different depending on who/what does it.  Most translations are confusing, meaningless, or funny.  I have a Japanese magazine with lots of vintage FG info, but many attempts with online translators have given me nothing useful.