I want to be really, really clear on this point: however you want to handle your situation is 100% your business, and NOMB. I have great respect for the kind and considerate way you and J are growing your relationship. I really do.
But from your descriptions of the situation, your husband seems to want little more than "to have his Kate and Edith, too" while you tenderly care for his insecurities and fears. And the basic unfairness of that is a trigger for me. I acknowledge this as my trigger and my problem, and certainly don't mean to imply that what I think should impact your situation in any way.
I just needed to express my outrage, that's all. Whatever you decide to do will be the right course of action, I'm sure.
I sincerely wish you the very best as you make your way forward.