Sometimes I mix baby food jars of fruit or vegetables or almond butter into his oatmeal. He's more inclined to eat almond butter than meat for protien. If I was you I would not feel guilty at all for feeding him stuff like chicken nuggets and plain carbs. From what I was told by a dietician its ok to feed him more of what he likes. If it's a texture thing he might like purees or food thats easy to chew or well blended smoothies?
Same boat, I try to remember that I'm in charge of what is served and he's in charge of how much he eats. I try to be playful, always let him steal my food, and just keep serving a variety of foods along with safe foods. His pass if he really doesn't want what we have for dinner is oatmeal with chia seeds (good nutrition boost) that he is in charge of making (adult adds the boiling water). Also, if you've got time homemade hand pies- sweet or savory go over great. I do unsweetened fruit with cream cheese or nut butter, butternut squash with ricotta and garlic, spinach and cheese filling. And you can do a large batch, freeze them raw and bake a few at a time.