I realise I sound like I'm pushing this now but I do think therapy would really help you at this stage, even if you go solo. As you say, you are involved, there's no way you couldn't be, you are married and any potential children could find him in the future and also you (assuming you stay together, I hope you do).
I strongly suggest you find someone to talk to, the impact on you is profound, that is clear from your posts, and you have not explored this, nor can you possibly explore this with your DH without it turning into an argument.
It's easy for me to say, as a stranger on the internet, without any understanding of your life, your commitments and what free time you might have, but I really think it would help you make sense of things, for yourself, if not as a married couple. It may be painful but I think the guidance would help you, it doesn't sound like it's going to get any better to be honest with you.
This thread has been a real insight into the consequences of sperm donation for couples. Those who have used or intend to use sperm donors will be grateful and applaud your DH's decision and efforts, but it's also important to hear your side of the story so thank you for sharing it. I hope you find some help. It's not your fault, you don't need to be a punching bag for your DH's frustrations or regrets and your loss abs grief is worthy of time to process it.
It sounds very much like the age cut off put pressure in you both but more so you as you didn't feel you could take your time to consider it and just agreed as it was what he wanted.