Eli, everything that is actual is trivially possible, according to every single contemporary analytic philosopher. I have no idea what you mean by "fundamentally possible", but I doubt you mean anything useful by it. If x exists, then it's possible that x exists. If x is an actual object, then x is a possible object. If you want, you can treat those claims as axioms. What's your beef with them? Surely you don't think, absurdly, that if x actually exists then it's not possible that x exists?

Allow me to attempt to translate (BTW, that a claim is so absurd is evidence it is not being made. Just sayin'.):

EY is not saying that some actual things are not possible. He is saying that things that are not actual, yet "possible", are exactly the same, as far as the universe is concerned, as things that are not actual and not "possible". Specifically, they are all nonexistent. Hence possibility is not fundamental in any ontological sense.

The general gist of the whole post is complaining that for all their precise logic, the people who invented modal logic have still not understood possibility and necessity. They formalized the intuitions about how possibility and necessity work, but didn't solve what they actually are (which is: labels applied by a decision-making algorithm).