If his text just said that he had a good time but he's made no attempts to plan a second date, he may not be interested in moving forward either. You can just say "Me too" and leave it at that; if he does take that as a sign that you want to get together again, then you can give your version of the "It's not you, it's me"--explain that you're not ready yet, even though you thought you were. Add some comments about his good points and that he deserves someone who's ready for a rel@tionship, if you wish. If it's possible you could change your mind after you've had more time to recover from your breakup, say so, but don't give him false hope if you really aren't feeling it.
As for your friend, you could say something like, "Mike was very nice and we had a good time, but I've come to realize I'm not ready to date again." I can't see her becoming angry over that.