I'm guessing he feels like he is under a microscope, and I guess in a way, he is. It sounds like you are a little too involved and know what he is doing and where he is every minute. I'm not criticizing, I'm just saying how it sounds. If you hadn't looked at his texts, would you be worrying about all this? No, because you wouldn't know about it. None of it is anything you can really do anything about anyway.
I know you're kind of on pins and needles with him just being out of rehab, but maybe you should step back a bit and give him a little breathing room. If he messes up you'll know and it won't be because you found out by snooping.