“When he announced that he was getting divorced the dynamics of their relationship changed. He had become possessive and now too available, he became to close and his designs on them running away together were not going to happen.”
The important part in there is really that his designs on them running away together were not going to happen. The fact that he divorced and was more available was only a problem because of his attitude and intention. Had he kept his wits and enjoyed his girlfriend as a girlfriend, the experience could have been even better than it already was for all three of you.
In the end though, this was a good experience for you two as a cuckolding couple. You now both know that she has the perspective and will to ensure your marriage comes first and is quite ready to kick to the curb anyone who wants to come between that.