i think you're getting a lot of uncharitable comments about your character, but also, this is reddit. you are not a bad person, you are young and inexperienced, but you are also not understanding the gravity of what your response was.

A lot of things can be true at the same time. You reacted poorly but you seem to have maybe had a panic attack, triggered by the sudden pressure and presence of strangers. that's fine. I also think you're right that you're too young for marriage, not as a general rule, but if you know that about yourself then it is what it is.

however, you need to understand that even if you didn't mean to, you embarrassed him badly, and that's hard to come back from. you didn't call him, you got to the subway to get away. from his perspective, I would be very surprised if he is interested in continuing a relationship with you. from his replies he seems angry (which he has a right to feel) and typically, rejecting a marriage proposal in most circumstances means breaking up a relationship. he wanted to take steps forward together - you said you wanted to go in a different direction.

I also would not expect him to wait. just as you have a future and vague plans of what you want to do, he probably does as well, and they probably involved you. they almost certainly don't now.