just checking... is he filling up on drinks like milk or juice?
I understand that stress in the kitchen, I get so sick of the refusals.
I would concentrate on slow and steady wins the race, and add a food each meal for at least a week before giving up. Make sure it's one you like as well so he sees you enjoying it.
I encourage DS to smell foods that I might have in the kitchen but try not to offer it to him to eat, I will also give him a food I don't think he'll eat when he's really hungry (but not really tired). So if he misses lunch and goes straight to nap (ie he falls asleep in the car on the way home) I give him lunch after his nap and he's alert and starving. He's more willing to taste something new.
You can encourage new exciting things, like dips for foods, such as cream cheese or tomato sauce. Helping to prepare meals in the kitchen. Also I found that both kids (though more my DD) like to 'steal' food while I'm cooking, or while I'm eating it. So sometimes I'll deliberately start eating a new food and walk into the room ignoring DS. He sometimes takes the bait and demands he eat it! He's tried a new food before he even realises! Getting them excited about food is hard work, but a big benefit.
DS was unwell and so we went from being OK with food, to hating food, to slowly liking food again. He's taken at least 6 months to enjoy and get excited by new food.
I've found he's funny too about some foods. ie he used to eat dried apricots, then stopped when he was sick. But if I buy the chopped up and packaged ones, he gobbles them up. Same taste, different presentation.
I personally would opt for trying to add formula to meals he does eat, or a multi-vitamin while you feel he's tired and not eating well. But also concentrating on adding more to his menu. I think as you say he seems tired, it makes us less likely to try new things as well. Iron might be a problem.
Can you add pureed steak and pureed green veggies to the meatloaf to add to his iron content?
He might like spaghetti bolognaise which is great for adding grated veggies like carrot and zucchini simmered down.