Wow! Many

to you. I'm so sorry this has happened to you.
If anything, I thought in the end, maybe you'd be the one to initiate a breakup. People grow & change. You both have been together since, what, 18 or 20-ish? That's a very young age to make such a longterm choice. Also very young to make a belief like both you and BF never want to get married. (Or at least a deeper form of commitment.)
You both were teens back then. It's actually natural for people in their 30's to start re-evaluating their life choices, beliefs and identity that they made & had since their teens and their 20's. People rarely stick with the decisions they made at such a young age. The philosopher, Socrates, said, "An unexamined life is not worth living." People grow or stagnate. Relationships need to grow or stagnate in alignment.
Either, unconsciously you felt him drifting away, and you suddenly wanted a promise ring as reassurance, or you've grown & changed and wanted more and he's unable to give it to you. He was right when he said the relationship came to a place where a choice had to be made, and he's realised he's no longer in alignment with you. Sorry.
As for you, although you don't feel it now, you are incredibly strong. You're heart ached for something it knows you deserve to have. If you weren't so strong a spirit, to have handled this possible ending, you would have ignored the ache. Instead, you trusted & listened to your heart.
While "someday" seems unfathomable now, as you just try to make it through today, know that someday, you'll love again. You'll be loved again. It will be the right love for you, as a stronger someone in your 30's, not the you of your teens & 20's. I'm not denegrating the love & relationship you had.
I agree with The Mystery Machine when she said you both came together when you
both had the same beliefs. People attract that which is at their own level. And that was who you both were at the time & for 15 years.
This is probably your first major breakup, especially of this magnitude. Go really slow with yourself. Be gentle with yourself. Don't make any major decisions. Comfort yourself a lot. Buy some chocolate, lots of comfort foods, and do some nurturing things for yourself.
I suggest you pick up this book
right away. It is THE handbook after a breakup or severe loss. You need time to grieve. This is written is short passages, which is about all you can handle. It is so soothing & comforting as it helps you go through the process & helps you understand what you are going through right now:
How to Survive the Loss of a Love - Make sure you get the Melba Colgrove version. There is another book out with the same title, that's not the right book. The
Melba Colgrove version is. There is a little excerpt on
Amazon.
And I agree with you for not picking him up from the airport.

This isn't about revenge. I understand he still has to live in the same house with you for now. It sounds like you're trying to handle this amicably, even though you are in immense pain. But, as a single person, especially the one who made the life choice, he's got start living as a single person now. And that means finding his own (single) way from the airport.

You aren't his chauffeur or his maid or his cook anymore.