Based on your post it does not seem that you had material grounds for them to reconsider.
You needed a death certificate which you do not have and also they do not believe your husband is with you for genuine reasons such as him not being able to recall your child's name.
Sadly, the officer was right in this case. Your best bet is for you to get the death certificate and then hopefully by then you both are able yo prove that based in the eyes of immigration you have a genuine marriage.
It was definitely not due to age, being married before or having children because other people have faced those barriers and gor thru.