"Only the present exists, Which includes nonexistence. [...] The possibility of existence or nonexistence."
Yes, there's only now. But it has nothing to do with the rest of your claim. I will sound like a broken record, but your use of the words existence and nonexistence is ambiguous. Or rather, you equate presence of forms with existence and their absence with nonexistence. However, when following your reasoning, possibility (which obviously must exist) predates existence and nonexistence. Thus, you are in essence talking about existence of existence and nonexistence, and it follows that what you call existence is not the existence.
"existence is unfathomable without its opposite"
How so? If nonexistence was possible, there would be no possibility for what you call existence or nonexistence. But as I said above, absence of forms is not nonexistence.
"Existence is change. Change is incomprehensible without no change, Another necessary unity of antitheses."
Not when we try to talk about absolute nature of reality. H2O is the same whether it's vapor, water, or ice. Even if it reacts with other elements or gets broken by electrolysis, the atoms are still the same. And so on and so forth. Change is simply change and it pertains to forms, not the actual nature. All in all, there are no antitheses -- e.g. touch can be painful as well as pleasurable.
"The concept of I is simply a manifestation or memory of a thing that was"
While I agree that "I" as a descriptor is a concept, it has nothing to do with memory. People with amnesia don't lack first person perspective. The same is true for children who still didn't internalize (associate) the concept of "I" with .. well, and this is the crux of the problem -- we learn to associate "I" with body-mind, whereas body-mind is in reality perceived by that which "I" denotes (thus body-mind is obviously not "I").
As I said previously, no matter how hard you try, you cannot reason out the true nature of reality. You must go beyond reason, concepts, and even the formless causal "realm".
