I liked what you texted! I think you did a good job.
I love that quote that a watched kettle never boils.
I am so hoping that your trip to Berlin is going to be fabulous and such a distraction. And will kick start a whole new attitude for you of concentrating on yourself and letting him figure himself out. (Give him space, even if you want to 'fix' his problems, including the gay friend thing.....).
Realistically if he is going to come back he will have had to figure out what has gone wrong and heal himself. And that takes time (so ignore your sister's advice she is just trying to help you not feel so hurt). And you wont want him back until he is really ready. If he has to go back to his hometown to think about things and re-group then that's what he has to do, and it is probably the best thing he could do.
