The insulator that you mention is already installed on your engine, it is underneath the rat's nest of pipes, hoses and wires. It was never meant to be installed right under the cover.
If this were true, I would think there would have been a massive recall for the thousands of Bronco Sports and Escapes that were shipped with engine covers to remove them. Lots of people have engine covers, and I havent heard of overheating problems.
I had the same problem. I finally gave it a quick hard upward jerk and it came off. It fits tight over the ball, but it will come off. Hope this helps.
As for the white plastic stud, when I had tried to buy it online, at least 3 dealers told me it had been discontinued. This was before it was determined that it is already installed on the engine, so there is no need to order it even though it may become available.
As the original early poster...