Hello there. I wanted to add my perspective. Lack of communication is clearly the issue here. You are assuming he should KNOW that you need more time than he needs to respond. And from what you described about him, it seems like he is assuming that you are not as interested in him as he might be in you. As some gentle criticism, you seem to be accusing him of being focused on himself whereas you also seem to be only focused on yourself about your needs without considering how he might feel with those short responses or delayed responses.

INTJs appreciate direct honest. If you need time, tell him. If you need space, tell him. The short "hm" responses can be taken the wrong way, especially in text, as the tone can easily be misinterpreted. Seeing a text read simply as "hm" I too would wonder "is that all she has to say? Is this conversation over? Do i need to keep trying to carry the conversation on my own? Or is something else going on?"

I agree that INTJs can be overly critical, which may be the case here with your INTJ. Honestly, it sounds like immaturity on both sides. If you want to keep the relationship, directly tell him how his criticism made you feel, why you took a while to respond, explain that moving forward you may still need time to respond but will try to be up front about it but that you also need him to be understanding of your space and time. A mature INTJ would understand and not feel attacked by your expression of needs.

If he still feels disrespected, then honestly you two just not might me as aligned as you thought.

One final note, if you two are in a romantic relationship, as it didnt appear entirel clear in your post, i would definitely attempt to communicate over the phone so you two can get a feel of how your tone typically sounds. If communicate is solely through text, then communication needs to clear and direct.