I can certain empathize. Sounds like you're feeling a little overwhelmed. Wife also surprised me with a desire for an open marriage after years together. I was NOT terribly enthused. It did get better.
I got the feeling that you're already feeling adrift from being in a new location (at her behest) and now you're being asked to remodel your marriage (also at her behest). Wow, that feels like a lot of compromise. I think you're fully in the right to say "I'm not saying never but I don't want this right now." I would encourage a small discussion (a couple months?) in the future so that she doesn't feel hopelessly stonewalled. Hopefully she can allow you some time to get on more of an even keel emotionally.
Right now, I'd focus on the panic attacks. When I've had anxiety issues, I had to force myself to focus of the facts of the situation rather than what I'm feeling.