FWB? Going back to friends?

Charlie • Bass playing bad ass with all too many questions
I talk to a guy on a regular basis and it started out as dirty talk but he really respected my boundaries and was always there before and after the heated stuff to talk in a more casual sense. 
He's three years older than me, almost. And he likes one of his friends (he lives in the state bordering mine so I don't get to see him and we've never been physical) and wants to ask her out. 
I agreed to ending the sexting because frankly I don't even enjoy
It as much as I pretend to. I just love making people happy so I do it anyways. But he talked about deleting the app we talk on because this girl is known to go through her boyfriends' phones and he thinks it would be a bad idea to keep the app, even if he clears the chat history. 
It just makes me sort of mad. 
How do I adjust to not being the number one girl in his life and focus on being friends? 
I also don't know if I don't like the sound of this girl just because he likes her or because she actually sounds like a bad girl for him. 
Kind of just venting. Please don't be harsh.