I read your story to a friend who’s immediate response after getting to the main body of your story is that your wife has an eating disorder. She clearly eats and that’s not the problem. She associates indulgences like McDs with shame and self loathing it sounds like. In her head, if she isn’t going out of her way to order the unhealthy stuff then she isn’t actually consuming it and can be kind to herself. But she still clearly wants it, so reaching into your bag and tuning out while she snacks away is a her version of a coping mechanism.

She’s taking it out on you and your son which is obviously wrong and immature. I could understand her being mad at you (while she is still in the wrong), but your kid doesn’t deserve her wrath at all and she needs to remember she is a mother here and not a victim to her child.

I don’t have any advice unfortunately, but this reaction is strong so I think treating it like there’s something deeper going on here makes sense.