Telling him I want a divorce and need support

My husband and I are both in our mid 30's and have been married for 4 years, no kids.

We've been in couples therapy for the last 10 weeks, which is the 5th time in the last 11 years. In therapy, we keep talking about the same issues and agreeing that we have come to a place where it does not seem like we can meet each others needs, and after each session, I feel like we're on the brink of ending things. My husband however will wait a few days and then start talking about long term plans, travel, projects for us to work on together and I feel so confused. He also refuses to discuss relationship outside of therapy so I haven't been able to ask him where he's at with all of this and gain insight.

Either way, I'm feeling very done. I'm exhausted. I feel sure it is the right thing to do, even though its the worst, most painful experience of my life.
I know that I cannot meet his needs and make him happy (he wants me to quit my job because it requires travel, but I love it and he doesn't work), and I know that he will very likely be unable to meet my needs long term. Neither of us are bad or did anything bad, it's just not working. I keep wanting to call it, but have lacked the courage.

I've been building myself up all week to get the words and strength to tell him in couples therapy. My fear is that he will feel blindsided by this (based on the long term planning convos this week) and I don't want to make it more painful than it needs to be. I'm also starting to doubt that couples therapy is the appropriate place for the conversation. I originally thought it would be a good place because we will both have the therapist with us as a resource to help navigate the hurt and guide an amicable conversation, but now I'm wondering if that feels to detached? Like is it more respectful to sit him down for a more intimate one on one?

Anyway, anyone who has been through something similar, I would greatly appreciate any words of wisdom.