Yes, Ferdinand wanted a peaceful life above all - hence he gave in to Maria Carolina to enjoy life and not be bothered by the duties of ruling and with her rages as well. That is very clear to me. But the mere fact that he gave in to keep peace indicates something was very wrong in their relationship and in MC's behavior/reactions.
Catherine II never pretended to love her husband but made sincere efforts - until the Peter made it known he wanted to replace her with his mistress and did not disguise his contempt for her - to conciliate and humour him for many years. This mostly happened when Peter went to her for consolation when his aunt, Empress Elisabeth, scolded him or sent away his favorites, etc. She said she felt sorry for him and understood the situation (being subject to the Empress' caprices and moods herself). She wrote in her memoirs that had Peter been a bit lovable, she could've loved him, despite his oddity, drunkenness, ill-humour, and offensive ways. She wrote that she knew how he was and if she did, she'd be the most miserable woman on earth. But she resolved to be a friend to him and wished for him to be the same to her. When the Empress was very sick, Peter came to her all alarmed about the succession and their chances, and Catherine assured her husband she had some plans and arrangements to keep them both safe. By the 1760s, the situation was either life or death - at the very least banishment to a convent - for herself and children so she seized power. By then, Peter III was all too eager to get rid of her, and who knew what would happen to her children (who were seemingly not Peter's)? I never saw that kind of sincerity from MC to make friends with her husband.....
You were the one who claimed MC was honest but there is not much evidence that she was; she clearly used deceit in her dealings, and as you pointed out, that was perfectly all right in politics. My point is that it doesn't seem right to assign an attribute to someone when that attribute isn't there. I did say she was only partly to blame for her disgraced state with her husband, and not wholly to blame. It seems you're so bent on defending MC and putting all the blame on her husband for treating her badly 1798 onwards, perhaps you can speculate ]on the ways in which Ferdinand could've dealt with his extremely difficult wife then.... Yes, it takes two to make a relationship work or not but a wiser person would have also known his/her limits and acted accordingly..... especially for consorts like MC, who, rightly or wrongly and like it or not, depended on the husband's goodwill.