1. I've decided the mystery woman in Sam's montage is Dr. Cara Roberts. They're more friends-with-benefits, but when she gets pregnant, they decide to raise their child together. They get married for insurance purposes. Cara dies first. When Sam arrives in Heaven, he eventually looks for her, and finds her with her first husband. "Carl and I, we found each other here and we worked some things out," she says. Sam gives her a big hug and says "That's amazing. I'm so happy for you." They still get together occasionally and reminisce about their life, their child. But then they go back to the person they love the most.
B. Anyone want to explain why Dean is not wearing the Samulet in Heaven?
3rd. Someone pointed this out to me on Tumblr, and anniespinkhouse brought it up here - is Sam wearing Dean's light grey hoodie when he cooks breakfast after Dean's death? Can you just kill me now, please?