[PetroniusMaximus]

"A lot of people (including some Protestants) don’t understand the suffering part of life."

This is a very shallow statement to make. Why single out protestants? Incidentally, many protestants learned about suffering at the hands of Catholics.

"We can suffer as Christ suffered (and even offer it up for the Poor Souls in Purgatory.)"

Salvation comes by the one time suffering and death of Christ o­n the cross. An individual's suffering may benefit his or her own character, but they have no value in paying for the sins of another.

Hebrews 7:27
Who needeth not daily, as those high priests, to offer up sacrifice, first for his own sins, and then for the people's: for this he did once, when he offered up himself.

Hebrews 9:26
For then must he often have suffered since the foundation of the world: but now once in the end of the world hath he appeared to put away sin by the sacrifice of himself.

Hebrews 9:28
So Christ was once offered to bear the sins of many; and unto them that look for him shall he appear the second time without sin unto salvation.

1 Peter 3:18
For Christ also hath once suffered for sins, the just for the unjust, that he might bring us to God,

[Campion]

but they have no value in paying for the sins of another.

Then God is not configuring us into the pattern of his son.

But we know that he is.

[A.A. Cunningham]

Incidentally, many protestants learned about suffering at the hands of Catholics.

You conveniently omitted that many Catholics learned about suffering at the hands of protestants.

[annalex]

An individual's suffering may benefit his or her own character, but they have no value in paying for the sins of another

The verses you quote show that the suffering of Christ is one time and unique, however, they do not speak of our connection to that suffering through the suffering in our own body, or to the sacrifice of the Mass. Other verses do:

24 [I, Paul] now rejoice in my sufferings for you, and fill up those things that are wanting of the sufferings of Christ, in my flesh, for his body, which is the church: 25 Whereof I am made a minister (1 Col)

24 ... Take ye, and eat: this is my body, which shall be delivered for you: this do for the commemoration of me. 25 In like manner also the chalice, after he had supped, saying: This chalice is the new testament in my blood: this do ye, as often as you shall drink, for the commemoration of me. 26 For as often as you shall eat this bread, and drink the chalice, you shall shew the death of the Lord, until he come. (1 Cor 11)