make things that can be individual. A while ago we made bread pizzas (pizza ingredients on a piece of bread, I mean), and I portioned everyone's out. My husband's 'pizzas' were 250 calories apiece, mine were about 100. that way you can mix and match what you want on it. Or make sub sandwiches, another thing that's easy to do. Also make a chicken salad and give him the high calorie dressings, nuts and meats for toppings, and go lighter for yourself. Or make basic dishes, say stir fry, and have the sauces on the table for adding, that way the calories are easier to work with.
hope that helps, I don't have a sick SO, but I do have one that needs to eat way more than I do.