I'm planning on telling my boss I'm leaving for husband's military job and reassure him that I am not leaving for a rival company. I'm not sure what to tell colleagues and friends and none will understand RE.
Why not tell them the same thing as your boss? It's true, isn't it? Either that or just say that you're burnt out and taking some time off.
I'm terrified the conversation will move to "how much money do you have" which I do not want to have with non-mustachians.
As you already noted, none of them will understand RE, so I doubt they'll process the fact that you have enough money to never work again. If it actually comes up, you don't tell them the number, just vaguely say "enough for now" or "husband still working", or turn it into a joke, "You'll let me borrow some if I need it, right?". But I'd be surprised if anyone actually asked this.
Plus I'm freaking out that I am freaking out and even through the math is right and D-day (or RE-day) is approaching, I am wondering if cold feet is just a sign that I am not ready for this life change.
It is a big change, so it makes sense to be nervous. However, it doesn't have to be permanent. If you decide later on that you want to go back to work, then do that. Remember
why you're quitting in the first place.
Unless you're up for talking about specifics, vague answers are best. And you can answer honestly, as you really aren't sure what you're going to be doing next year or the year after that. Granted, they'll be asking about work and you'll be answering about non-work, but that's the beauty of it all. :)