I am so sorry to hear of your TTC struggles. I don't have a DH but I have a DP for us it was no question really, I mean sure we were scared and had some uncertainties but we new we would still travel down this road. I think the one thing for us was we just wanted to be parents and we didn't care how it happened we just wanted it to happen. YKWIM?
I think sometimes DH's just need a little extra time. Do you know anyone in real life who has adopted? Was it a positive experience? Maybe you could talk to him from that perspective, like hun, you know so and so adopted look how happy they are maybe we could just do some research and go from there.
Also have you looked into donor sperm? They do amazing things there like you send in baby pictures and they will match you with a donor that has the most similarities to your DH. I can imagine this is very hard for DH he probably feels let down with his body and then like he is letting you down he may need time to grieve before looking at other options. Good Luck and keep us posted.