Hi Mom2GSG I just came accross your post and could not leave it unanswered.
I had my first child at 39 after a couple of years of IVF. When we tried for number 2 we failed and after over 6 years of IUI/IVF/IVF with donor eggs, we started the process to adopt. We now have an adoptable 4 year old boy (who joined our family) by adoption and a 10 year old birth daughter.
I can't really comment on what is right for you and your husband, your family, except to say that two children are a lot more work than one, for me, but worth it. If you as a family can afford to increase your family, what is your husband's reason for not wanting more, other than the fact he would be in his 70s when they graduated? Personally, I would say, he may or may not see them graduate, but my son is only 4 and I am very nearly 50, as is my husband. If my son goes to university, (no certainty he will) and if he goes at 18 (no certainty he will) and if he graduates three years later my husband and I will both be 67. It doesn't bother me and it might help you in understanding why it bothers your husband.
It may be finances he is thinking of, or it may be that you will return to work if no more children arrive, or will not if they do etc. Only you know. But if money is not an issue and you don't need to go back to work then I wonder why he is so set against it. In fairness to you and the child you share I think he should consider it.
No one should be forced to have a child but by the same token so one should have to deny that desire if it is realistically possible.
If you want to heal your heart you may look at counselling or a charity such as the Infertility network, which might apply to you after your experiences.
www.infertilitynetworkuk.com
This may not be the right charity for you, just an idea.
If adoption every does become a possibility for you, please join us on the mumsnet adoption threads.
The other thought is to put your passion and love for children into charitable work etc but to be honest I would not want to start 'doing' anything until you have dealt with the powerful emotions underneath the situation.