First things first. YOU. You are first, if not, there will be nothing of you to help care for him. Find a co-dependent group. This kind of group teaches you how to care for yourself AND stay sane while you live with another who you cannot control.
That said, the one thing you most likely have control over is the food menu. Create a menu of dinner meals for the month (to take away the stress of what to fix) and repeat meals are fine. This is easy to do when you make a list of your favorite meals and then insert them into a calendar. Use the same menu for each month. Don't repeat a meal in the same week.
The menu needs to consist of as few of non-processed foods as possible (i.e. no instant or quick fix anything). Vegetables for every dinner meal, frozen are just fine but not canned unless that is all you have. Roast all meat in a roasting pan on a rack. Our carbs are pasta, brown rice (easy to cook in a rice cooker and is very tasty), or multi-grain bread for hot sandwich dinners. We don't like to mess with fish so I buy albacore tuna in a can (it is of higher quality).
We use the plate method for portions, 1/2 veggies, 1/4 meat or other protein, 1/4 carbs. I am diabetic, my husband had high cholesterol and this is a great way to eat for health and eat foods you like. We shop once a month and break our meat packages into meal servings. We spent about $200 US dollars a month on food for the month. We save a lot of money shopping according to our menu.
Beyond this, don't expect him not to be depressed. You'll be disappointed and it will show. Keep a record of his moods on a calendar to look for a cycle. Use an up or down arrow to do this. Log events like visitors, pay day, etc. This can influence a depressive's mood.
Encourage, but don't nag. Love, but don't be at his beck and call. Sometimes it's through some suffering that a person will say to their self that they are tired of this and look for a solution.
If he says thinks like: if I had this or that, DON"T get them for him. He has to do that for himself. I say this because wishful thinking is entertainment for all of us. I use to do this and my husband would get mad because he really didn't want it.
I wish you all the best.