I think you're going to have to let it go. You have no control over him at all. You can make requests and negotiate boundaries so that the pacing is okay and you feel somewhat pushed, but comfortable, but that's about all the control you have.
He could date this woman on his own no? Why have a triad? Nothing in the poly hand book says ALL poly relationship dynamics should be FMF unicorn situations. I would love to know why this seems to be thee situation to strive for for most poly people who come into poly as a couple? (Sorry, that is to the greater audience and another thread topic). There are many options. Maybe you will find that you are interested in dating men at some point. Especially as you are not bisexual. Maybe a threesome with a man would be fun. Shake it up a little ya know? The men don't have to have sex, but you get all the attention