Guys have their own brand of tease talk, and your BF may have felt that his friend's comment was stupid & didn't deserve a response. In that context, he didn't care ... who would?

My impression remains that you've got a lot of living and laughing, dating and growing to do before you're going to have matured to a level to make life-commitment decisions. Once you settle down (& for) the domestic live, so much of the rest of your life is limited and decided and not available to you. Why rush that? Why not call off this engagement, which doesn't have your best interests going for it now, take a deep breath, and figure out who you are and what life you want. Then go get it.
You sound like such an exciting gal, willing to reach out and grab on to life with both hands. Why not give yourself the chance? Who knows, you might do something important!