Don't know about your first 2 questions.

Old La Honda is better than La Honda, less traffic. It has some steepness to it. Good job avoiding Hwy 92, do not be tempted by that one, it's very busy and dangerous.

In Woodside, Mountain Home Road is better than Woodside Road.

After you get the top of OLH and cross Skyline, you descend, and the intersection with La Honda warrants care, you'll be descending steeply and you do need to stop at that stop sign.

There's a store in San Gregorio- it was featured on a TV commercial during one of the recent bike tours - I think it was the Colorado tour, where there are two guys standing in front of a store messing around with their phone/computer thing which was the product being advertised.

Alteranatively, you can turn off La Honda at Pescadero Road which has less traffic, this does add a climb, but it takes you through Pescadero, where the country store has some of the best baked goods on the coast. SEriously do not miss this store. You can also get there off Stage Road, which runs between San Gregonio and Pescadero - I prefer this to the coast, less traffic, and it's nice scenery. It's hilly.