yeah i'd throw some emergency equipment in there. extra tube(s), CO2, lube, spare tire, extra electrolytes.. whatever you might need but probably won't.
if you like what they are serving at the rest stops i wouldn't worry about food or drink mix.
but yeah depending on the road to trail ratio of this thing 6 hours might be a kind of a optimistic time estimate unless your FAST. then again if it is 50% or more paved maybe not. in a true offroad 100 mile race the winners usually take like 6-7 or so hours even on the easier courses.
oh yeah, fresh gloves! sometimes that is like a little bit of heaven.