Hi, unregistered
This is a really tough spot and I really feel for you being in it. I think it is very courageous of you to have tried the lifestyle - but it is unfortunate that you did so only to please him. I wish that all couples who ventured this way were genuinely excited TOGETHER about the prospects.
As far as I know - we don't have any marriage counselors here, so please take whatever advice you get with that grain of salt. We will all simply tell you how we might respond in your situation, but our advice has never been FDA approved
If he is threatening to leave you over this and this alone, then my response to him is to grow up. Nothing irritates me more than the "I'm taking my ball and going home" mentality. Using divorce as a threat or in any other way seeking to "punish" you for not playing along is childish. Does he not realize that wives who are willing to swing are incredibly rare? They aren't easy to find. Dumping someone that he is otherwise in love with, in hopes of finding a woman who will swing, is stupid.
You gave it the old college try...
It wasn't for you...
It isn't for everyone...
I know that right now you are very scared of losing him over putting your foot down - but bravo to you for doing it! Swinging is something that you both have to want and be comfortable with - and your relationship has to be rock solid to enjoy.
You've put the ball in his court and now he has to decide how this plays out.
Spoomonkey