I agree, you can't sit and analyse everything. You just have to move on with your own life, otherwise, you will go insane.
Like you say, you don't see where it went wrong between the two of you, so you should be happy that it wasn't you personally that was the problem, it's him, his job, his image etc. Those are things that you can't control, so there's no point in analysing things that you have no control over! I also don't think that you should sit and wait for a text from him saying he has changed his mind, it might never come.
When you told him he had a month to decide, you might have just given him a reason to get out of the relationship altogether - when the month is up, he might say "my feelings are still the same so we should go our seperate ways", and he doesn't really have to explain anything else to you, because you set a deadline.
All you can do from here is focus on yourself. You are the only thing you can control, so focus on making yourself better.
Like I said, you will only drive yourself crazy over analysing everything.