Sure, tucking into a meal a little before everyone else is a bit rude but does not warrant the verbal abuse you say the father of your grandchild directed at you.
His reaction sounds as if it was way out of proportion. Perhaps I've missed something but did no one tell him to calm down at the time?
Or it is more than likely that if he gets this emotionally dysregulated over something relatively minor, he would also kick off if asked to pull his head in, therefore others generally walk on eggshells around him?
I am making an assumption here but I think asking someone who acts like this for an apology is like a red rag to a bull. I totally get why you wanted one. But I also think his response was also highly predictable, given that he doesn't seem like the greatest guy, having got your disabled and presumably quite vulnerable daughter pregnant (as you mention a few posts later).
I don't think you deserved the treatment you got from him at the meal, or his abusive text response. But I'm not sure you could have expected anything different. When people show you who they are, you're only going to stress yourself out (and your wife) if you keep on insisting they should be different from how they generally are.
I get that you want your wife to be a bit coldly civil to him as a show of support for you, but ask yourself how that in any way helps the relationship you have with your grandson, in terms of the trouble his father may have the potential to cause.
It's obvious you won't get what you want from him. And any apology, should it ever be forthcoming, would likely be empty.
Focus on your grandson and his needs and don't let his father live rent free in your head. He is the way he is and you wanting him to meet your standards is only going to give you a heart attack.
Take the high road. And good luck.
I'm not underestimating that it's probably a very challenging situation all round.