I did look at your route and specifically in the Sonoma County area. I think you're making a big mistake to leave the coast at Skaggs Springs - Stewarts Point Road. It's one thing to do that road unloaded and questionable to do that loaded . . really questionable . . there are no services between the coast and Lake Sonoma, and that includes potable water sources. And there are many stretches that are 10-15% grades for many miles, some that are exposed. We use this road for an obnoxious double century called the Terrible Two and the Terrible Two's Bad Little Brother. While only ~36 miles, you may wish you had gone further down CA 1 and taken CA 116 and some other backroads to reach CA 128 through Healdsburg.
Here's a link to a ridewithgps route map - look at the elevation profile from mile 107.3 to 143.3 http://ridewithgps.com/trips/1417561 and you can make your own decision. Best of luck.
Retired Terrible Two Director
Santa Rosa, CA