It is very possible that your husband thinks that he is saying something supportive. There are many ways to interpret those words, and his intention may be to support you the best way he knows how. That doesn't mean you're getting what you want or need, but it also doesn't mean that he isn't trying to care or be supportive.
For example, he may think he's saying: "I want you to know that I love you and care about you no matter how this birth plays out. You seem very worried about the details, and I don't want to add to the stress and pressure of having things go a certain way. I want to know that you and the babies are healthy. Birth is a mysterious process that I don't understand. You seem very concerned about all the details, and I find it helpful to just focus on the end result."
You may hear him saying: "I don't care about how the birth plays out. This is too mysterious and weird for me to understand. Why are you getting so worked up worrying about something that has about a million variables that are out of our control? Just focus on the outcome."
My DP and I had a lot of this when preparing for my birth, so I can relate.
Can you coach him on how you want to be supported? Sometimes things that are obvious to us are not at all obvious to our partners. Rather than asking for his support in a general way, you may need to ask for something more specific. For example, "I need you to help me think through what we'll do if situation X arises." Or, "I need you to listen to all my fears about the birth without making any comments, and then hold me and tell me that you'll be there for me no matter what happens."
Having a great doula is a great idea. I am all for getting support from the people who are best equipped to give it. It is a lot to expect our partners to be good at everything.
Good luck, mama. Birth worries take up a lot of emotional energy. Be gentle with yourself and your hubby.