Your husband is a contrarian and my mother is a negative person: she has a glass half empty outlook. Very depressing to be around. Feels very disheartening to anyone who thinks or feels positively. The constant repetition of your husband's contrarian and my mom's negative outlooks can be very depressive to us, the caregivers.
My siblings tell me to ignore my mom's negative comments and to let it go in one ear and out the other but it doesn't work that way.
I hope you are able to step away from your caregiver role at least once or twice a week because your husband's contrarian outlook does affect your well-being and mood. I have been trying to protect my own outlook by leaving the house for a couple of hours or even taking a short walk around the block. Is there anyone who can relieve you so you can take in the fresh air and get away for just a little while?
Another thing I'm trying is to go in and out of her room often and for different reasons so our interactions are short, giving her less time to complain. I go in and take her blood pressure and then leave the room and tell her I'll be back soon. Next time I go in I ask, would you like a bowl of fruit? Then I leave the room and come back 15-20 minutes later with her snack and then say, I'm going to walk the dog and I'll be right back. All these shorter entries into her room prevent long conversations but keep me connected with her and lessens her negative comments although I still get them but at least I don't have to hear her comments at nauseum. Good luck and God bless you!