I'll break down each point in order. It's often easier to see the problem with an argument when you examine each part carefully.
Note that this Mormon argument's part A uses the word "Divine" to refer to God. I would use the word "divine" to refer to angels as well but angels were created. Therefore I will substitute the word for clarity below.
A. If God is the essentially uncreated and the only one of its kind, then Christ cannot be fully God.
- It is possible for a single person to be at once both fully human and fully God.
Yes. As a Christian I do claim this to be true. Hebrews 2:17 "fully human in every way" and Colossians 2:9 "For in him, bodily, lives the fullness of all that God is.".
- Human nature is such that it is essentially created at some time.
No? The argument hasn't defined what exactly "human nature" is. This premise is not obvious enough that I can accept it at face value without such a definition. While the Bible does state that Jesus was human, it doesn't go into details on the requirements for being considered fully human. Human bodies are created and Jesus did have a normal human body for a time however this doesn't make him stop being God. Modern Christians have the Holy Spirit which is timeless but doesn't cause us to stop being human. Most human souls are created but if this argument is trying to claim that "to be considered a human you must have a spirit that was created and Jesus doesn't have such a spirit" then the counter is that neither of those 2 statements are confirmed by the Bible and as such they may or may not be true (I'd argue false and true but that doesn't matter).
- God's nature is such that it is essentially uncreated and timeless.
Yes. It is true that God wasn't created and has/will exist for all time. See Genesis 1:1, John 1:1-3, Revelation 22:13.
- A nature defines what is essential to the kind that an individual is.
This statement appears to be a definition of "nature" however terms should be defined before they are used. Additionally this "definition" doesn't accomplish anything since I still don't know the requirements for human essence.
- It is impossible for a single person to be both human (created) and also God (uncreated) natures. (From 1, 2, and 3).
No. Yes it is impossible for a single thing to be both created and uncreated but humans are made of multiple parts. My human body was created but the Holy Spirit in me wasn't created. I'm not sure if this argument is asserting that humans don't have souls at all or if "to be considered a human soul it must be created" but I'll disagree with both.
(65) Premise #4 entails the denial of #5 and therefore one of them is false.
Not really? Premise 4 doesn't appear to be saying anything at all. Point 5 (which is a conclusion rather than a premise) states that there is a contradiction so #4 doesn't need to be here in order for #5 to state what the problem is.
B. If God possesses essentially attributes that humans cannot possess essentially, then Christ cannot be both human and divine.
- God is essentially omnipotent, omniscient and omnipresent (essentially good, immutable, impassible, timeless, a se, etc.)
For simplicity, this is true.*
- Jesus Christ was and is fully God/divine.
Yes. Colossians 2:9 "For in him, bodily, lives the fullness of all that God is.".
- Jesus Christ was and is fully human.
Yes. Hebrews 2:17 "fully human in every way"
- Necessarily, no human is omnipotent, omniscient, or omnipresent (essentially good, immutable, impassible, timeless, a se, etc.)
No I don't agree with this premise because, in fact, I can name exactly 1 human who is omnipotent: Jesus.
Whatever God's nature is, human nature essentially cannot be / Whatever God's nature is, human nature must be essentially different.
This is a logical fallacy called "begging the question". The argument has done nothing to prove the claim that a human can't be omnipotent. It effectively says "assume that no human is omnipotent (#4) therefore no human is omnipotent". This is also called circular reasoning because (despite the other premises) it has just gone in a circle and accomplished nothing.
*If you want to get technical (and off topic) it's a little more nuanced than that. Omnipotent: God is truth, he can't lie. Therefore there is something that God can't do. He can still do everything that matters but doesn't fall into the omnipotence paradox. This doesn't contradict scripture but explaining how would be large enough for its own question. Omniscient: yes: past, present, future, and even alternate timelines (Matthew 11:21). Omnipresent: he can influence anywhere but Jesus is in a single location. The Holy Spirit can be in multiple places (every Christian) but isn't everywhere (not in non-Christians). The Father is in a single location. Immutable: there are verses where God "changed his mind" (eg Exodus 32:14) although this change would've been determined ahead of time and as such is getting really off topic...