Can you get to big meadow campground in a large motorhome pulling a car.

Yes, you can. Look on the G, H, I loops for "pull-through" sites that can accommodate larger vehicles.

Yes, at some sites

Yes, they have pull through sites.

We had a smaller motorhome, get a site as soon as possible, they don't have a lot of longer spots.

I've seen RVs at Big Meadow camp ground.