What can one say? I can only begin to imagine the loss of a child like that, and my mind shuns entertaining the idea. You have my deepest compassion.
My own experience of coping with the loss of someone deeply important to me is, after time, that the power of their memory comes back, and all the ways in which they changed your life and the lives of others stay with you. IMO, the pain of the loss of someone so important does not go away, and nor would I want it to, but it does transmute into something that can continue to touch peoples lives in a positive way, including your own and that of your partner.
I only wish I had something more to offer you.
Adam