Hi, phantazmagoria, here's to hoping I can answer some of your questions...
First off, congrats on what sounds like a pretty great situation of everyone talking to everyone, everyone dating everyone, and hopefully to all three of you having time together, too...
#1 question: Her and the Husband have had sexual relations without me, but not vaginal, penetration sex. I know they both want to, just waiting for me to say "go", and where I don't feel much pressure, I do feel guilt.
What do you feel guilty about?
How do I get to a place where I'm totally fine with this? They only thing I can think of is just to let them do it, and see what happens, but that sounds so risky!
I gotta say, this seems to be the approach that will work best. They're already fooling around, happily so, and respectful of your desires. That's awesome, and a skill you three shouldn't lose. Also, they want to go further, and if they do that with respect, and you do it with love and compassion for them, then just let them go there.
Are you afraid of where it might lead? Why would this be risky? Are you able to do things with her that he can't? I'm going to guess that this is a situation of opening up, because you and your husband can do things together that she can't do with him, and perhaps not with you. What pathway do you see to being a real triad that can honestly intertwine?
And is that the risk? Of losing something with your husband because of his (and your!) involvement with someone new? I'm going to guess that you've already changed your marriage in subtle ways - making those public is a lot less risky than keeping them hidden away...
But again, I'm just guessing. If you could talk more about "risky" and "guilt," that would be really helpful...
#2 question: How does one become totally comfortable with their third seeing other people outside of the triad?
You say that she wants more than she can get from being in this triad, but it also sounds like this triad includes space where she can't go, yet. Is that a permanent choice? Are you really seeking a triad, or are you seeking a playmate on the side? (Either one is fine, as long as you know what you're seeking and what the consequences of that choice are.) If you see a pathway toward a balanced triad in which she has meaningful relationships that fulfill her, maybe you'll end up in a closed, fidelitous relationship. But if she's feeling left out and wants something you can't give her, for whatever reason, then she's in her rights to seek a relationship like she really wants.
Sounds like communication on this is going to be meaningful and important.
One recommendation: don't call her a third. That puts her on the outside of your couple. That, or accept that your husband is a third to your relationship with her, and you're the third in his relationship with her. I really dislike that phrasing, because it implies that the "third" is the one left out. It doesn't have to be that way, it can be an enjoyed space where that couple has something awesome, and because you're dating them both, you get to enjoy the awesomeness they share with each other.
How do I get to a place where I am cool with her being with other people?
Based on your first question, are you cool with her being with your husband? That sounds like a strong place to start - you're scared of where this might go, it seems, and also wanting it to go places you haven't articulated yet. You like her being monogamous to the two of you, but you haven't wanted her to be together with your husband. Am I reading that right? because it could be that she needs security that she doesn't have, yet.
I feel like I'm supposed to be totally fine with them having sex alone AND her having sex with others .... but how??
Aw, man, I don't know of any "supposed to's" when it comes to triads and poly. There's what works for you, based on ungodly amounts of communication. What do you really want? What does your husband really want? What does she really want? In what way are you happy together, and what will you have to change to find the happiness that you seek? Those questions are real, and difficult...
For all that my answers ask for clarity and such, I'm not critiquing. I think communication is key. I think openness and honesty and inclusiveness are key. And remembering that a triad is way more complicated than couple-and-a-third is key. (It's impossible to say that you're half of a couple, but she's a third of it all... that's a recipe for her to feel less. All of you are one third of something larger, now, and your thirds combine into two-third segments, and the whole of you is much larger and more intricate than what you had before....)