1) I like camping at the rec center a little better, it's got a pool and a hot tub. It's super quiet during the week, too.
2) Depends on how hard you're climbing. Some of the classic moderates, like the grand wall, diedre, UE, will have a couple of parties on them every day in the summer. If you're on slightly harder routes, like Freeway or something, you shouldn't have to worry about lines.
3) Mt Garibaldi is right there, it's a biggish mountain.
4) A nice compromise between liberty ridge and rock climbing would be the complete north ridge of mount stuart. It's a bit of an approach, but the climbing is super fun, and definitely alpine. 50 classics for sure, and the weather can be more dependable than Squish.