="Philosopher19"](1) There is existence/x exists
(2) Everything that exists, does so only in existence
Here you are setting yourself up for a fallacy of equivocation . The equivocation is between "existence" in the sense that things do, as a matter of fact, exist (which you're useing in #1 and the first part of #2), and the human concept of existent (which you apear to be using in the second part of #2). So either your #2 is saying "things exist only because things exist", which is tautological and would render the step superfluous, or you are saying "things exist only within our concept of existence" which is false. Things have been existing long before we and our concept of their existence came along.
[quote="Philosopher 19"\ (3) We are fully dependent on existence[/quote]
That's true in the first sense of existence: We exist and therefore are fully dependent on things existing. But it's false in the second sense of "existence" Stones, for instance, have no concept of existence, but they exist just fine without having such a concept.
(4) All minds are limited to what existence allows
You've got to be kidding, right? Our minds can behold all kinds of things that don't exist, and that existence wouldn't allow. Just go to an art gallery with surrealistic paintings in them You'll sww some.
(5) Given 4, anything that is either rational/comprehensible/understandable, necessarily belongs to existence (existence accommodates it
That's false as a consequence of your #4 being false. I have no problem comprehending, understanding, or reasoning about pink unicorns farting rainbows. They just don't exist. And thus, your point #5 is refuted by demonstrating a counterexample.
(6) Omnipotence and omniscience, are rational concepts that we have an understanding of
Which puts its existence on exactly the same footing as pink unicorns farting rainbows.
Only Existence/that which is all-existing/omnipresent can be almighty/omnipotent and all-knowing/omniscient
Sure, only something that exists can know everything and do everything. But that doesn't mean anything
that exists can do it, and the rest of your argument contains nothing that woulsd demonstrate that.
Thus falleth apart the rest of your fancy syllogism.