For me, this isn't about whether the third party is an ex. As anyone who reads my posts would know, I firmly believe in staying friends, even GOOD friends with exes where possible. In fact, I commend the OP for starting out with an open minded view towards his bf being friends with an ex.
However, I still see the bf's behaviour as very problematic. It's just plain disrespectful to spend that much time talking to a friend when they are supposed to be having together-time with their partner. Unless the friend is having a genuine crisis of some sort, together-time should be just that - together-time. Without others intruding. I would feel the same way no matter who the third party was.
A friend of mine has been having an ongoing crisis for the last month and a half or so. I've been spending way too much of my time being support person number one. But when I'm out with Sir and I get a text from her, I say 'Sorry, I'm out with Sir, can I call you tomorrow?' She usually sends back something along the lines of 'Oh okay, I'll talk to you then'. And that's it. The rest of the night is for Sir. If it's extremely important she MAY get a 10 minute chat, but then I have to go. Because that time isn't hers - she gets to have me the rest of the week :tongue:.
It's a respect thing.