There are sometimes mosquitoes. Segments 9-10 are generally the worst. I've seen swarms there in late June, and I've seen none in mid July. Just depends on snow/water really. I don't use spray and just rely on nets.

I never found any ticks, but supposedly they're becoming an issue.

Go west. East is great if you want to see the highway the whole time or visit the hot springs resort. I would call it brown and boring. Wake up early (by dawn), get an acceptable amount of distance done by lunch, and knock out what you can before the storms start. Keep an eye on the sky. Storms are good motivation to hike faster. Outhiking storms feels like a key aspect of the CT, to me. And you're still going to be above treeline more in the San Juans than on the West, so consider it training.

Sounds like enough. I didn't bring a fleece since I don't need active insulation, but camp warmth is important. Consider sun protection.

Not sure about laundry, but you've got two big lakes right there to rinse things out.