If you mean if you guys do get together, then oddly enough, I think you're lucky that you've gone through all of this hell.
Because when you do talk with him, then you now have this experience to refer to when you bring up how much communication and openness is necessary and important. The proof of what can happen when a couple isn't communicating is right there for him to see, and neither of you are apt to ever forget all of this. When he does inevitably go quiet, because these habits are hard to break (but they are breakable), then just refer to these days. Tell him the relationship is important and you don't want to repeat the same mistakes. If he's INTJ, he should relate to that well. They don't like repeating mistakes. (NTs just don't like that.)
We'd much rather learn from them.
And, if he doesn't choose to give it a go, then hey, you've got this experience to refer to in the future no matter who you choose to be with. You know how important communication is now, so you'll be much more aware of when it's needed no matter who you are with and that relationship will be much better for it.
As for learning to read them, that just takes experience with them. Making them feel safe when they do open up will help make sure that they will open up more easily in the future. Caring, just caring, enough to watch how they are under different circumstances is all it takes to learn when they're probably bothered.