This is a really interesting thread and you've posed one question that I've been asking myself lately - where does poly end? How much is too much?
But anyway... I digress very slightly...
I've only been poly for two years and I can definitely says it's a huge learning experience and a steep curve. What you think you want now can change over time, but if there's one important thing I've picked up along the way, it's that we are responsible for getting our own needs met
It's easier said than done. You meet someone you really click with and you hope that they can fit the specification of what you need in a partner. Sometimes communication, growth and time can alter things to a level playing field and a very happy compromise is formed. However, sometimes you just cannot get what you need from a person.
In terms of your GF, I can understand both sides of the coin. On one hand, I can see where you are coming from and it's absolutely reasonable to want the things that you want from a partner. On the other hand, with the exception of my primary GF who I could talk to all day long, I am like your GF in the sense that I would be happy talking to others on a less intense basis. I can understand her need for time alone.
A few questions come to my mind about your GF. Does she have any other partners that take up her time? Where do you all see each other in terms of a relationship fit? Do you think of your husband as a primary and her as a secondary, or do you not believe in hierarchy? What does she feel and believe?
Being a person that does not need or want daily contact from someone who isn't my primary... I am wondering about one thing. I truly do not mean this rudely and your GF may not even find this an issue - but, if I feel like I don't need much contact and another partner of mine keeps texting or messaging me, I feel claustrophobic... then I want to get in touch less and less. Typically, when they don't get in touch, I find myself missing them and am much more likely to want to contact them more often. Strange way that the brain works.
Is there any chance that your GF doesn't want to get too close and is keeping herself at a distance, or does this really not seem to be the case?
Moving on to your thoughts about dating other people.... I think this is very fair. Poly dating is like any other dating and therefore, why settle for something that isn't completely fulfilling you?
As for the STD/no sex thing... I understand her fear of STDs and I understand the no-oral rule, since we have the same guideline in our relationship, unless protection is used. But... if protection is used and everybody is honest... and they request proof of STD testing before sleeping with new partners, plus getting regular tests themselves... then really, there should be no reason not to sleep with others, unless you all agree to a closed poly triad.
I also understand your fear that you will keep wanting to 'collect' because of flaws. Sometimes it can work the other way around... i.e. I accept people as secondary partners that I wouldn't choose as primaries, because they take less of an active role in my life. For example, my last secondary is a bit self-obsessed and jabbers on incessantly... it would drive me mad in a life partner, but I find it entertaining in a more casual secondary.
I think that you should definitely have a talk with both your girlfriend and your husband and get your thoughts out on the table again. You've gotten this far with figuring out what you want, so all you need to do now is communicate it. Experience will help you find out exactly what you are looking for, what fits and feels right and how many partners you can balance.