Where is your bottom line minimum?
Do you have to be dating other people to be happy? That is one thing.
Do you have to be given support/nurture in your polyside expression? Like you share your books, movies, thoughts, feelings and can be ok in a closed duo IF that expression to HIM is allowed? (ie: you get love and understanding as a poly person from HIM, but don't need another lover) That is another thing.
But seriously? Right now? Poly stuff set aside for a moment?
Even in a monoamorous situation? Your partner is showing no interested in your inner life or giving you emotional intimacy. You are burning out on that.
Your interesting book could be about baking. And you send him websites about cool cake decoration. And are asking him to come to your bake sale sometimes. And he does... nothing.
Not much back and forth relating going on there.
What's he want out of this? What's he willing to put in? Talk to him.