I can relate to some of the behaviour you describe in your husband, but cannot speak for him, of course. I do not share his background of abuse, but come from a family and social background where emotional expression was discouraged in men, seen as a feminine trait.
From an early age I consciously decided to practise the sort of emotional suppression you describe and by my teens it had become a destructive habit, though I was unable to see that.
After suffering psychological problems, I realised I needed to develop skills in emotional communication. It took me many years to unlearn the bad habits I developed in childhood, and some things I may never correct.
Bereavement is especially difficult. Learning to express love is easier because it can be practised daily and there is often a positive and immediate reward, emotional and/or sexual, to reinforce the new behaviour.
By contrast, dealing with loss may only happen every few years and there is no immediate payback for expressing grief. This can make the old mechanism of ignoring and storing the painful emotions a more appealing option than opening up to them. Personally, I fight hard to hold back tears at funerals but will cry for a few minutes once I am alone. It is the public exhibition of weakness I find deeply uncomfortable.
Unless a person really wants to change this, they cannot be pushed into it. Your husband might benefit from counselling, but he has to decide that himself.
Meantime, you may just have to learn to live with him as he is. These deep-rooted coping mechanisms are deeply ingrained and unlikely to change unless he becomes motivated to tackle them.
It is encouraging that he has attended some joint sessions with you, maybe that would be an easier path for him to follow?