If he gets into his head as much as you said (the comment about his retreating into his little cave with his stresses, etc), then why don't you take what he asked you at face value?
It doesn't sound like this guy stopped caring about you. It sounds like he is a mess himself and maybe didn't want to put you through that any more. So he texted to see how you are doing. Not to keep tabs on you, but because he honestly cares. He may also be trying to get you to ask him how he is. It may be a bit of a cry for help, but I don't know him to know for sure.
As of right now though, you are single. Don't overthink his actions and just concentrate on your own.
Good luck.
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