1) Mr. Ramsay and Mrs. Ramsay take different approaches to life, with Mr. Ramsay relying on intellect and Mrs. Ramsay relying on emotions.
2) Only Lily Briscoe finds a way to preserve her experiences through her art, hoping to order and connect elements in her portrait that have no relation in the real world.
3) The lighthouse symbolizes different things to different characters - it can represent hope or frustration, and James comes to realize it has competing images that both contribute to its essence. Nothing can be defined by just one thing.