He berates St. Alphonsus while praising “saints” of the heretical & schismatic sect of Eastern Orthodoxy in his article.

I thought that guy was going to be taking a break from the internet? Darn, that didn't last long. Oh well, we suffer on ...

I guess this difficulty would not occur if God kills everyone when they reach that number immediately and they did go straight to hell without delay.

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I think the idea is more that the person will become hardened in sin and lacking the grace to repent. Don't quote me on that, though ...

Okay, but remember in the famous sermon on this topic about Voltaire, St. John Vianney said that Voltaire did repent and was sorry for his sins and spent his last hours begging for mercy and apologizing to God, but it was too late for him, for God had abandoned him and he had to go to hell.

Yeah, I saw this on twitter. Don't see a problem either way. One can disagree with St. Alphonsus.

But it's not just St. Alphonsus:

1. St. Basil, St. Jerome, St. John Chrysostom, St. Augustine and other fathers, teach, that as God according to the words of Scripture, "Thou hast ordered all things in measure, and number, and weight" – Wis. 11:21 has fixed for each person the number of the days of his life, and the degrees of health and talent which He will give him, so He has also determined for each the number of sins which He will pardon; and when this number is completed, He will pardon no more.

https://www.olrl.org/snt_docs/num_sins.shtml

Beside this paragraph, St. Alphonsus explains what he's talking about, while Skojec appears to have been too slothful, and didn't even look it up.

St. John Vianney said that Voltaire did repent and was sorry for his sins and spent his last hours begging for mercy and apologizing to God, but it was too late for him, for God had abandoned him and he had to go to hell.

But there are many kinds of FALSE repentance (i.e. I'm sorry that my sins have caused me (and not God) suffering) and FALSE sorrow for sins.  God reads all hearts, so He would know Voltaire's true sentiments.
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Besides, we don't know that Voltaire is in hell.  God could have forgiven his sins, but not provided him a priest, as a punishment (i.e. lack of Extreme Unction = longer time in purgatory).  Or, maybe God (in His infinite wisdom and mercy) did not send a priest because He knew that Voltaire needed to be scared of hell, and to experience desolation.  If a priest had come, Voltaire's sorrow might have been less or too casual, or not genuine. 
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On the other hand, St John's point with this story is that we cannot and should not wait for our death bed to convert.  As Jesus told us in Scripture, "Not every one that saith to me, Lord, Lord, shall enter into the kingdom of heaven: but he that doth the will of my Father who is in heaven, he shall enter into the kingdom of heaven"
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Since St John is not here to explain further, what we can say is that God forgives all TRUE repentance and sorrow.  Only God knows who that applies to.

But think of it this way, people are always scolding people as scrupulous for thinking they sinned too much to be forgiven, but if what St. Alphonsus says is true, they are not scrupulous, they are correct. It is too late for them. So priests should be telling people in confession, "I am sorry but your sins are too great, they cannot be forgiven. Try to have peace for a little while before you die and are damned and do not commit too many more sins because that will increase your inevitable sufferings in hell. But I can do no more for you. I am sorry. For every man has a number of sins beyond which God will not pardon, and you have passed that number."

No priest has ever said this kind of thing.  You know you've reached your "final number" of sins, when you're dying.  Then it's over.  Before that, if you still have life in you, God has given you mercy.  But you can die at any moment, even an hour from now.  So treat every moment as your last.