Oh you poor loves. Many heartfelt condolences to you.
You must feel like your heart is splitting into a million pieces.
I agree with joint counselling and I suggest separate counselling for both of you actually. You are going to need each other, to support each other through the stages of grief.
You feel completely shut off from life and don't want it to continue, your husband probably feels his grief too but like you say he tries to put on a brave face.
Denial
Anger
Bargaining
Depression
Acceptance
That's the grief process and you may not reach them in that order. Sounds like your OH is at Denial and is instead, placing the problems at your relationship. So instead of saying he is upset at your son's passing, he is instead transferring and projecting that unhappiness onto your relationship.
I wish I could say it will get better. I wish I could say when. But I can't. All you can do is learn to get through the days.
Please don't bottle up or deny your feelings - it will only come out some other way.
Finally, I'm still not sure on my own beliefs about afterlife and such, but I have always liked to believe that the people will lose sometimes check in and watch over us. I like to think that because you carry a piece of them in your heart, they are always with you. You will never forget your son and he will always, always be with you.