You seem supportive of your wife in a really lovely way.
My husband is much like you: supportive, loving, happily mono. We have been together for about 8 years. I started a relationship almost a year ago with my girlfriend Mya, who is also a bisexual married woman. You might enjoy reading our blog over here
My husband has experienced some insecurities and feelings of discomfort. Mostly it has just felt strange to him to be in a poly situation. And he did have to shift his mindset when it became clear that my girlfriend became an influence on our future plans. Also, it was sort of sad for him to see me infatuated with somebody else, and know that it's something we can never experience together again. At the same time he felt very glad for me, a lot of compersion. And our relationship has grown and benefited significantly, we both agree on that. Now that the situation has normalised he hasn't been experiencing any of the feelings of strangeness, he is just happy to see me happy.
It has been extremely satisfying for me to explore my sexuality with my girlfriend. And having another really happy relationship, as well as the whole opening up process, has made me appreciate my husband in a completely new way. It is so often that poly relationship lets me experience concretely the importance he gives to my happiness, and I love him for that. We have both become more independent, and I'd say more loving and committed to each other at the same time.
The best advice I can give is not to be afraid of having some uncomfortable feelings, be willing to talk about things, and be understanding and compassionate towards each other while being clear in what you want and need.