Husband is losing too much weight

My husband is 67 years old, a former sheet metal worker with cardiomyopathy (weakening of the heart muscle). He is 6'1" and weighed around 200 before he got sick, 9 years ago. Five years ago he started losing weight drastically and dropped down to less than 140. The doctor told him to "stop losing weight." Big help. The nurse suggested drinking Ensure Plus 3 X day. We did this for about 6 months, along with regular meals, no dieting, just the stuff we normally ate. He slowly gained back some of the weight and stabilized at 158.

I am 59 years old, 5'7", and have been overweight most of my adult life (highest non-pregnant weight was 194). By following low fat/calorie diet most of the time, I lost about 20 pounds. I maintained the 172-178 range for the past several years, but still had a big belly. Last fall my son introduced me to the idea of grain-free diet. I started reading and listening to various podcasts, and then decided to give it a try. I cut out wheat and sugar from my diet. I've since lost another 20 pounds (in only 4 months, not 4 years this time) and I've gone down 4 notches on my belt, for the first time since before I had babies, 25 years ago. Yeah!

I do all the cooking, and he likes the food I cook, eats decent amounts at meals. But he had started losing weight again. He is now at 138, which makes him way too skinny, not just thin. He looks like he is starving, but says he feels fine.

I've tried adding in rice and potatoes to his meals, extra butter and olive oil, peanut butter, etc. He is still losing weight. I want to lose another 10 pounds. I wish I could give it to him! I just don't know what to do to help him reach a decent. weight. We are not in a good financial situation and cannot afford the Ensure Plus (plus it isn't real food anyway). I need some ideas for him that won't sabotage my own results.

I haven't used the food tracker here (I sometimes use one on SparkPeople), but here is an example of what we eat:

Breakfast:
2-3 eggs cooked in butter or olive oil
Sauteed or roasted vegetables
Fruit

Lunch:
6-8 oz chicken (pork or beef)
Salad with vegetables and olive oil vinaigrette

Dinner
6-8 oz chicken (pork or beef)
Sauteed and/or roasted vegetables
Sweet potato with butter

Snacks:
Roasted nuts, like pecans and almonds, and seeds, like pumpkin and sunflower (I do the roasting)
Cookies made with honey, not sugar, and a non-wheat flour, like almond flour or oat flour
Cheddar cheese sticks (I cut the cheese into sticks myself)
Fruit and Yogurt or Cottage cheese