Jane,
I suggest a third option: have an open and direct conversation with him. It was a good first step to let him know you are feeling unappreciated and unhappy with the status of your relationship, but unless you’re leaving something out in your posting, it seems terribly vague. Feeling unappreciated could mean a multitude of things from “you never thank me when I pack your lunch” or “you don’t tell me you love me”, for example. I think in order for you to make any well-informed decision about your relationship, you will need to ask him where he sees things going. Does he want to get married again? Does he want kids? Don’t assume he wants to be a “free bird” until you hear it directly from him. Now, if he’s told you that he never wants to get married or have kids, you have to take him at his word and act accordingly. But don’t do anything rash based on a “hunch”, even if your gut tells you something. You owe it to him and your relationship to at least have a serious conversation before arriving at a decision. For what it’s worth, I don’t think a year and a half into a relationship is “fast track” in terms of having these types of conversations.

I am a bit concerned that you didn’t feel he was being genuine when he listened to your concerns. Do you have personal experience with him that makes you feel that way, or is it perhaps a result of your insecurities that you’ve described within the relationship? A healthy relationship involves a lot of open communication. You might think he should just “know” to text you the next day. Perhaps many people in his position would have. But he didn’t, and there’s nothing wrong with you telling him how that made you feel. If you want to marry this man, you should probably start feeling more comfortable having difficult conversations. I believe it will only serve to bring you closer together. If you can’t share your feelings with your partner, what kind of relationship is that?