Would it be possible to do farmer's walks with two barbells? It's ages ago now, but before we got farmer's walk handles, I recall some of the lifters at my gym doing farmer's walks that way. And yes, probably squat day, or an upperbody day that isn't right before a squat or DL day.
Alternating weeks between strength and maintenance could work. Although I think a better set up would be where one week you go hard with the main movements, and easy on the accessory/supplemental work, and the next week easy on the main movements, and more volume with the accessory/supplemental work. I mean, you shouldn't be having to moderate the intensity/volume of your training that much, you're not an old man yet (right?), even if you have particular limitations/considerations.