There are a lot of mistakes people make in relationships as they discover polyamory. It sounds like you are willing to try to work past some of your husband's mistakes and still try. That is a very tough decision, and I think it can work if everything else falls into place.
When someone's partner is on a date with someone else, the standard advise I hear it to find something to do for yourself. Don't stay at home and obsess. Do something fun like take a relaxing bath. Or break out some snacks and watch your favorite DVD. Or go out with some friends.
Another thing is you should let them know what you are feeling. You can tell them, that you are working very hard at trying to trust them. You can say that you want to feel more loved. Polyamory works for the most part on communication. Say what you desire and be willing to compromise and work together. Passive aggressive behavior is very poisionous in a poly relationship.
You are also dealing with NRE (new relationship energy). It lasts about 6 months to 2 years. Basically, it is the honeymoon period of a relationship. If you can see that this stage is temporary and it doesn't mean anything bad about your relationship with him, it may ease some of your worries. He should also realize that he is in NRE and monitor himself to an extent.
I think reading some books on poly will help all of you. It will provide some good tips. It can also lead to discussions you need to have, but are having a hard time bringing up.