It sounds to me like this "first attempt at a poly relationship " was fostered from an episode of your husband cheating on you a while back ..?? That's not exactly the best approach to starting on this path I so- no wonder you aren't exactly feeling any deepe connection. What do YOU want? Poly relationships are not strictly a guy and two women.. Ask yourself if he would be OK if the roles were reversed. Not to say that this arrangement won't work out- if you are both genuinely committed expanding your relationship and you desire/ need a connection in order to proceed then get out and find the person that is right for you.
She and your husband have thier relationship, you and your husband have yours, you and (someone?) have another relationship, maybe there is a another connection there that I don't see.
The point is that you have to decide what you want and need. Once you are comfortable with that and you and your husband have discussed this , then go and get it.
It really doesn't sound to me like you need to be worried at all about your husbands feelings or this other woman's - I sounds like they are quite comfortable as is.