///To speak of a mere partial corruption of man, one in which the lost sinner is only spiritually sick in his sin, makes a misdiagnosis that grossly diminishes the grace of God.///

That’s a BOLD assertion, considering what Christ Himself said:
Mark 2:17
“When Jesus heard it, he saith unto them,
They that are whole have no need of the physician, but they that are sick:
I came not to call the righteous, but sinners to repentance.”

Many stage 4 cancers are terminal, where if you have it then you are essentially counted for dead. Sin is very much like cancer. Once we have it, it spreads and if not cut out, it will consume us.

///Likewise, to espouse a conditional election that is dependent upon God’s foresight of man’s faith corrupts the grace of God.///

Again, BOLD assertion probably based on a former false presupposition.
Jesus is God’s Elect, and we are then made elect through our faith in Him, which comes by hearing the word of God, and believing unto righteousness (see Romans 10, the whole chapter).

///To teach that Christ made a universal atonement, making salvation possible for all (though actual for none), cheapens the grace of God.///

Christ reconciled ALL things to Himself through His finished works on the cross, even the “false prophets” who “privily shall bring in damnable heresies, even denying the Lord that bought them, and bring upon themselves swift destruction” (2 Peter 2:1)

All who sleep will be raised at the resurrection of the dead, though who keep the commandments and believe on the Lord Jesus Christ will be raised to eternal life, and those who continue to live in unrepentant sin will be raised to shame and everlasting contempt. (Daniel 12:1-4, Revelation 22:14-15, 2 Corinthians 5:10, etc.)

///To believe in a resistible call that allows for the free will of man compromises the grace of God.///

Absolutely false, God is love, and love by definition must be “given” it cannot be “taken”. We love Him, because He first loved us. We respond to His grace freely BECAUSE He chose to love us while we were still in our sins. We being the corporate “whosoever will”, not individuals cherry picked before creation.

God has commanded ALL men EVERYWHERE to repent. He does not command things that are not possible, and if we have not sinned and have need of saving, then there would be no reason for the call to repent. So all sinners have the ability to repent, and God has commanded us all to do so, but we tend to be stiff necked in our pride, which is the whole purpose of the Law, to break our proud hearts through knowledge of sin, so that we humble ourselves to seek His grace. God resists the proud but gives grace to the humble.

///And to think of reversible grace, which would allow man to fall away from the faith, contaminates the pure grace of God.///

Nonsense, let God be true but every man a liar. We are called to endure in our faith to the end, believing unto to the saving of our souls, not turning back to perdition. But some do fall away, forgetting that they WERE purged from their old sins. (Hence 2 Peter 1:1-11, and Hebrews 10:35-39, Matthew 24:11-13, etc.)

///These views undermine the grace of God, and because of that, sad to say, they rob God of His glory…///

Nothing can “rob God of His Glory”, we are completely unable to save ourselves apart from the finished works of Christ on the cross. He is the one who saves, and who sets the requirements for who is worthy to be saved. Even when we are faithful to do all that is required, by repenting and keeping His word, we are still unprofitable servants who do not “deserve” to be saved, but He has chosen to forgive us of our past sins anyway by His grace. Grace is grace because we do not deserve it. Salvation is a gift because it simply cannot be earned or taken, just like love, it must be given.

///To whatever extent one deviates from any of the five doctrines of grace, one marginalizes the glory that is due to God alone for the salvation of sinners.///

False. They simply reject the flawed logic of men by accepting what clear scripture teaches.

One of the great points he makes that connects to your fourth point is: “It’s fine to label ourselves, but I think it’s wise and kind to avoid labeling others. No one likes being put in a box. (I am always amazed to hear people tell me what I really believe!) When it comes to terminology, especially in conversations regarding God’s sovereignty and meaningful human choice, I’d recommend using our definition or understanding of terms in place of the terms themselves until we know we’re on the same page. It may take longer to explain, but we’ll know what we’re really talking about.”

Defining terms as your opponent defines them is helpful in promoting the kind of graciousness you’re encouraging.

“Be not carried about with divers and strange
doctrines. For it is a good thing that the heart be established with grace;
not with meats, which have not profited them that have been occupied
therein.” (Hebrew 13:9) If it is not of God, it does “not profited”. If you ask them what
benefit is there in believing this, they will usually respond by saying, “It’s
the truth”, but people on both sides of any argument believe their side is
right. But the question remains, how does it profit Christians? If someone
believes there is a hell, he is much more likely to get saved, and also be
concerned about his loved ones and friends getting saved; but if he does not
believe, then “let us eat and drink; for to morrow we die.”

Things that are believed have an effect on us, for good if true, and for harm
if false. For 40 years I have been asking those who believe this belief, what
profit is there in it? The only real answer I have received in all this time
was that they say it takes away all pride from man, as he has nothing to do
with it, but salvation is already “not of works, lets any man
should boast.” (Ephesians 2:9) Besides, people can have
pride about anything including saying, “I’m elect”. One Christian I knew who
came out of Hyper Calvinism told me it appealed to his intellectual pride.

Even those who believe in this
doctrine already know there are possible problems (sometimes serious problems)
associated with it. It has split churches and more Bible colleges than any
teaching I know of! It is also used by some as an excuse for not winning souls.
After all, if God wants to save them, they will be saved even if I do nothing,
and If God does not choose them for salvation, then according to their belief,
no matter what I do they will not be saved. But Paul said, “Wherefore I take you to record this day, that
I am pure from the blood of all men. For I have not shunned to declare unto you
all the counsel of God.” (Acts 20:26-27) Why would Paul say a thing
like that if it did not to some degree depend on him? See The Layman’s Biblical Handbook http://www.thelaymansbiblicalhandbook.com/predestination.html