From what I have seen, triads are very hard to maintain because it is hard for everyone to feel the same about each other. People change. Feelings ebb and flow. And if it doesn't work, it can be explosive.
I think what works well, is for each relationship to work itself out without being forced. Maybe your husband will just be good friends with a new boyfriend of yours. Or maybe they will be lovers. But I would advise not to force it and just let it happen.
It sounds like you are doing some good communication so far with your husband. Keep that up. He sounds like he is trying to be open minded and wants to see a more concrete example before he can fully decide on how he feels.
I would suggest reading some polyamory books. They are good at helping people deal with jealousy and communication (two biggest areas of polyamory).
You can look for any local polyamory groups. Maybe your husband will want to go to one as well since there are quite a few monogamous people involved with polyamorous people.