I wouldn't want to spend my life with someone who pretty much says they have to date (sleep) around just to be sure I'm the one (ie good enough).

If he were head over heels for you, there would be no doubt and he would have eyes only for you. He wouldn't want anyone else. He would just KNOW.

So now he wants permission to go out and find out if there's someone better than you?

I think the writing is on the wall. I think the relationship is over. I think that you don't want to lose him so you're telling yourself this is a good thing.

I'd tell him that this isn't a "break" rather this is a "break UP". Tell him that you will be dating other people and moving on with your life. Maybe later he'll realize exactly what he's lost, but do you really want someone who had to go out there and see if the grass really was greener on the other side of the fence, only to discover that it wasn't and that you're as good as it gets? (Read, he thinks there are better things out there but wants to keep you as a back up plan.)

Don't settle. You can do better than being someone's consolation prize.