Killington can be tough anytime, let alone a holiday week! Don't worry though, there's plenty of terrain, it's just very crowded. The problem, IMHO, is uphill capacity. There are so many ways up the hill, the trails get very crowded. Keeping your distance can be a challenge. I had a pass there for 10 or so years and haven't been there in quite sometime, (~ 7 yrs). Back then, there were usually ways to find something good to ski when elsewhere gets skied off. I assume things are somewhat the same, although I hear it's more crowded.
Definitely start early, eat early or late, and ski thru lunchtime. Take your lunch with you if you can and eat in whatever lodge you're near at the time, there's plenty of them. We always were first up and first to quit, as the place can get skied off in an amazingly short amount of time, especially the steeps.
Pico is not connected.
Next time you plan to come to the states for a ski trip, consider our west, (Utah, Colorado, California, Montana, etc). If I had to fly to get to a destination, I would not ski the east US. Our snow is very unreliable and your chances of a dump are significantly less than out west. I'm not saying you're guaranteed great conditions in the west everytime, (I've seen it bad a couple of times), but they get lots more snow as a rule. For a few quid more on the plane ticket and a few more hours in the air, it's usually well worth it!! You have to rent a hotel/condo and get a car anyway, why not increase your chances for a good time?
Look at our holidays more closely and avoid 'em. We can get stupidly crowded too!