You might need to start looking for new friends. If they are originally his crowd and you still feel like an outsider after all these years, it might be a sign that this is not the right group. He was flirting? Ew. How embarrassing. He said he is heart broken and doesn’t want to live without you yet he is partying and dancing away. Dancing like doing actual dance moves with a partner? Or just drunken clubbing? I like to visualize. I’d probably laugh. Uncomfortable. He probably showed up because you told him you’ll be there. Don’t tell him anything