Well, you could look at this situation and call it a massive emotional cluster%$#@ (which would be an accurate assessment). Or, you could choose to think about it a a really intense learning experience. Like ripping off a giant emotional bandaid. You're dealing with trust issues, jealousy issues, safe sex issues, boundary issues, and all while trying to really shake out how poly is going to work in your family (or even if it will).
The big thing I see here is trust issues all around. Hubby broke trust when he cheated last spring, and honestly I'm not sure everyone waited long enough before jumping into poly to build up the kind of trust that let's an established couple open easily (if it is ever 'easy'). Wounds like that take a long time to heal, and it sounds like you are still not healed from it. Plus, besides the infidelity, he exposed you to potential harm by not using protection - another trust blow. Now, if you redact your invitation for him to date GF, you will lose his trust as well. He won't be able to trust you to honor your word, or to actually be honest to him and yourself about what you're really feeling. As I'm sure you know better than most, trust is really hard to get back once you lose it.
Since you say he is handling his sadness over your intensity with BF well, and he is trying to grow emotionally without putting too much burden on you for his jealous feelings, I suggest you do likewise for now. If you ask him to call it off with GF because your jealousy is too intense, it would be more than fair for him to ask you to do the same with your BF. Based on the information here, that sounds like a lose-lose-lose-lose for everybody. Personally, if I felt about someone they way you describe your feelings for BF, I would gladly battle some yucky feelings to keep that relationship in tact. But that's just me. Another viable alternative would be to call off the poly and focus on rebuilding your primary relationship until it is on more solid footing. It wouldn't be my first choice, but its not a bad one either. Only you can determine what is best for your relationships.
Trust is rebuilt slowly, but it needs opportunity. Make sure hubby knows how you are feeling, and that this is an opportunity to rebuild some of the trust he lost. If he can't be 100% faithful to your new arrangement (that is, whatever boundaries you set, but safe sex and total honesty at an absolute minimum), then he is not ready for this arrangement. But, he does need some chance to prove himself, IMO.