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If you feel that there is no other way to make things work out, then you have to do what is the healthier thing for you now. If you're not heard and there is nothing that can be done with this living situation, the relationship may have exhausted its flame.
For any relationship to work out, there had to be not only compromises made by each partner but also working together to find a resolution to a problem. From what you've shared, this does not seem to be happening. You know your limits and what would work for you. It's not selfish to have told your partner about it and in asking for some other options. Maybe he wanted a care taker for his kids rather than a partner?
it seems that you're already thinking that he's detached emotionally and seems preoccupied w/ his son.
You've been thinking for a while now about moving out. You can tell him out of courtesy that you're leaving. If he really is emotionally uninvolved in the relationship, you'd know for sure by his reaction. Either way.
As far as whether or not he cares, you seem to sense that he does not based on his behavior of not being able to communicate properly with you, seeming unconcerned for the relationship and more for his son (or at least you say he's putting on a front). This may be a situation where he can't juggle a relationship and taking care of a disabled child at the same time. When did this all get to this point? Is he able to work/do his music and help you at all now?
It may be good to discuss this with him now before you make any plans. It is something that has to be addressed; there may be some solutions that come to light while talking about this objectively with him. You seemed happier at the beginning of the relationship and too quickly things appear to have changed. It's fair for both of you to try to figure it out before calling it quits.
Giving them some time may help clear his head.