Hi,
Others will chime in as well, but here are some comments.
The route passes very near Cloverdale on the way back. Should you desperately need something, all you need to do is cross over the freeway to get to the 24 hour minimarts. Further on, there are at least two stores in Geyserville, and I've stopped there almost every time I've done the 400k. There is at least one store on Fulton that was open late, but there are likely several that are just off the route a short way.
The bridge is supposed to open the west side at 5am. Best to check the GGB website to confirm. I know that the west side was open on our Fleche when we came by at 6am, and closed when we came back on the 400 WR last week at 4am.
I would never trust elevation gains stated on ridewithgps. The "about 10800" figure comes from reports of riders having done the ride. That is a better ballpark number I would say, certainly between the two sources you name.
rob