First of all, you seem like you're handling this really well. I mean, I haven't been there for your discussions, but in your writing I see a gentleness and a bravery.
It seems to me that your husband went a little berserk on testing boundaries, that he might be one of those people who needs to step over limits to understand them... and that he may have gotten a little high on the new-person-to-sleep-with thing. He may be a little addicted to it. And he may be ashamed of that addicted, ashamed of his new sexual freedom, and deeply afraid of losing you and probably pretty conflicted about his actions.
Yes, he acted a FOOL.
But that doesn't mean you ability to communicate is broken.
How is he behaving now? Do you believe in his devotion to you? Does he understand the multitude of boundaries that he crossed? Is he even asking for forgiveness? Is he trying to re-earn your trust?
You guys can work through this if it's what you really need and you will come out with an arsenal of new knowledge and deeper love.