Some quick thoughts. Group activities are a great way to meet people, like classes, hiking groups, etc. Okcupid is one good, free online dating site that's poly friendly. And maybe there's even a poly social group in your area that you could find by searching online.
In terms of the jealousy, maybe this site will give you some helpful thoughts... there are several great essays on the topic: http://www.morethantwo.com/
Three girlfriends plus a wife is a LOT. He must be a busy man! Make sure you and he have enough time together to feel fulfilled, make sure you have dates out with each other.
So, two of his gf's are married but don't identify as poly... do their husbands know about your husband?