check out this site.
Missouri state motorcycle laws
it appears that ur buddy is all good to go... there's no state law for turn signal/Horn at Missouri.
dont worry about non dot approved on Led.. theres a bunch of'em on the bikes now days.. I would'nt worry too much about it. just make sure the led light is visible on the rear. just get it inspected and enjoy the ride...
by the way the pics on the bike is sweeet!... loved the color on that bike...very creative..
Cheers...