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Hey,

It's understandable that you still care about him even if your romantic feelings for him have changed. I can tell you are a good person for not wanting to leave him alone to find a new apartment and things like that. But you're right that he is an adult and his own person. He does have some experience with moving from moving to City A with you, so maybe that's some experience he can use when he goes to move himself. But you're right when you said that he is an adult. It's not your responsibility to fix things, especially since it would mean being tethered to him when you need a new start. You don't deserve to be stuck where you are unhappy just for someone else's benefit. I can't tell you what the right answer is about breaking up in September or right now, though.

If you have the energy to do so, maybe you can find some resources or guidelines that he would be able to follow when he goes to find a new apartment or when he does other things he will need to do, so that way you can present those things to him and he has a starting point he can go off of. That way he's not totally on his own without help but you're still able to get away from him. But only do this if you have the energy to. I understand that it is a lot of effort!

When you do break up with him you can remind him that this doesn't mean he is a bad person or did anything wrong but that you're at a point where your paths are different and you have different ideals for life. That happens with adults sometimes, where it turns out your lifestyles are just too different, such as with him wanting to play video games all the time where you want more growth. It doesn't mean either one of you are wrong, it just means both of you deserve to move on to find people that do align with your needs. Be firm with him and tell him you'd appreciate it if he didn't try and change your mind or say that the feeling will pass, and that you would appreciate it if he respected your decision.

If you think no contact with him will be hard I'd also block him everywhere you can after you've broken up with him. Again, it's not because he's a bad person, but it's because you won't see any messages he may try to send you and you won't be tempted to message him somewhere and reconsider breaking up.