The blue vase in the disassociation scene was from Sassenach (2014) when Claire saw it in the window in Inverness.
The rabbit that Claire sees when she is held captive refers to Jamie's vision when he woke after Culloden. He saw snow, the rabbit and Claire. It symbolized life. The seer Margaret in season 3 had a vision of that rabbit.
The title shares itself with a song by The Association. The song originally came out in 1967 and is considered the most commonly played song on the radio and in television in the 20th century.
Jamie's words to Claire when he rescues her from the Browns ("You are alive. You are whole.") are the same words that he said to Roger in Famous Last Words (2020): "You're alive. You're whole. All is well."