It's so weird but I have the same issue, my lo suddenly just stopped saying mama a few months ago unless he is really upset. He will point at photos and say papa, grandma, grandpa etc but not mama. Apparently he does say mama a lot when I'm not around. I don't know the reason but I've seen multiple posts on here about this which makes me think it might just be a phase or something.
My LO has never said mama, he says everything but and when I ask him he just laughs at me. I don't think there is anything you can do but please know that that baby needs you so much, I'm sorry you're having problems with your husband I hope those can be resolved and you can start the new year in a better place.