I hope you can finish this sentence: He has been evaluated by a competent professional (not his pediatrician) and our plan is...
You and your W need help in navigating this. You're right, all kids have a different relationship with each parent, it's meant to be that way but what you're describing goes beyond that. At one point you said something like "he escalates this" as if he had a choice. He may not.
You mentioned a couple of things and I'm paraphrasing, he likes things a certain way and having trouble with food early on. That might be nothing, might be something.
This isn't my area of professional expertise but I have some personal experience. It is what it is, personal experience but when your kid has an issue you do tend to learn everything you can about the subject. My S21 has OCD and it's not what many people, especially those who insist on saying "I'm so OCD!", think it is. It's not being a perfectionist (although that can be a feature) and it manifests sometimes very differently in kids. I ignored what I was seeing for a while and then tried to talk myself out of it for a while. He was 13 when we finally had him evaluated and we could no longer ignore it. I was in deep denial. My son was hospitalized for a week to get his symptoms under control.
S21 was a challenge from birth, what some would call high needs. When he would have meltdowns, it would be with me. It's been described to me as when the anxiety builds so high and they don't know how to deal with it (let's face it, they can't smoke, they can't drink, they can't do any of the other things adults do to "manage" anxiety), they meltdown and that release happens with the person they feel "safe" with. He still comes to me for the emotional part of his life. He has a great R with his Dad but he can't let that side out with him. I get the full-spectrum of S21 and that's good.
I'm not suggesting your son has OCD but he's suffering, don't you think? If he were doing what he does and complained of pain anywhere in his body, what would you do? Sometimes kids don't have the words to describe what's going on, especially at 4.
As I said earlier, all this may be something, may be nothing but wouldn't it be great to be able to help this little guy and make your family life better? You can get help in learning how to help you child deal with his emotions.
What they learn at 4 will make them more prepared at 33, right?
Me 57/H 58 M36 S 2.5yrs R 12/13
Let me give up the need to know why things happen as they do. I will never know and constant wondering is constant suffering. Caroline Myss