1. 30-50 mph
2. Nope. But doable (I don't think I've ever actually seen a cyclist on 152 over Hecker Pass)
3. Good question. I'm curious too. I'm pretty sure I've heard another option that involves dirt (but road bike friendly dirt).
I have seen cyclists on hwy. 129 which is a few miles further South. Not much of a shoulder here at some points either. Traffic is a bit faster since it's more flat/straight.