I totally get the wanting to be loved and understood bit. My longer thoughts there.
BUT you couched it like this:
DO WHAT FOREVER?
- Not share you inner life?
- Stay in a close polyship of 2?
For you might mean #1, and that you cannot be happy if you never get to share and express your inner life to your husband.
But he may have taken it to #2 fear place. So he thinks you telling him "I'm here for now but later I want to Open. So let's keep talking so I can arrive there one day because I cannot be with just you forever. "
And if HE is feeling like "NO. Not going there!" then it is natural for him to NOT want to cross the bridge of talking more and be more open to vulnerable because he's already feeling pressure/under attack. If that talking bridge is going to Open Land or he THINKS it is. So no he's gonna be a clam.
If Open Land really is where you want to go that is one thing.
But if you are happy as a poly in a closed polyship of 2 with your mono spouse if he allows you the expression of your inner life at least (thoughts, feelings, etc) then that needs clarifying
to your husband and maybe some reassure/support to boot.
And then maybe he'd relax a bit more and not close off into defense clam mode and give you what you are after -- more emotional intimacy, talking heart to heart, etc. Which is what you need to feel happy in a closed polyship of 2.