I've gotten enough of a look at the first video on my phone that I feel that it is about as borderline as it can be. I could understand ruling for or against it. There was probably enough room to get the entire truck inside without going below the yellow line, but he still went below the yellow when he attempted the pass, and then he was pinched down there after he got there.
Could that pass be made legally? Probably.
Was that pass made legally? Probably not.
Was he squeezed down? Definitely.
So, who is at fault? I have no idea.
The trucks are heavy, and with a full lead draft (192+ mph), they can sway from side to side pretty hard when turned. I can't see what shape his tires are in, but if they are bad, that might also have caused some of the side-sway that put him below the yellow line.
What would you do if you were him in that exact scenario coming out of turn 4 on the last lap? Would you turn down for the small opening on the inside, push the truck in front of you, or try to swing out wide (which looked blocked)? I can't say I wouldn't have done the same thing he did.
However, I would have tried to stay on the outside of the yellow line under all circumstances. I would have made the car in the middle have to physically force me below the yellow line, so that I couldn't be blamed. It's your call, and it's not an easy one, as I see it.