You're in a sober/safe house now, O. It seems to me, after you involved this guy in your dramatic entry to rehab, he maybe feels somewhat responsible for checking up on you.....BECAUSE you keep replying to his texts.
As you put it, you reply because it's 'rude' not to do so. I don't agree, If it were me, I wouldn't reply every day, because he may feel you're 'encouraging' him, or may worry that you've become dependant on his daily texts? Who knows? But replying doesn't seem errr, necessary?