My partner sounds a lot like yours. I have just soldiered on. I got tired of eating fatty things, so I started making things that were more on the borderline between what he thinks is healthy and what I think is healthy. I make a lot of salmon and lean meat items. I only use bacon as a flavoring. When I do serve something sort of fatty I remind him it's grass-fed so has all the heart healthy Omega 3s. I serve simple dishes of meat and vegetables. Often I serve him rice or bread on the side if it seems like it would go well. I will sometimes make him pasta, too. I try to make him feel like I'm not forcing too much on him other than general healthfulness. He is microscopically slowly moving in my direction as far as diet goes.
Female, 5'3", 49, Starting weight: 163lbs. Current weight: 135 (more or less).
Starting squat: 45lbs. Current squat: 160 x 2