Hello and good morning! I was hoping someone could answer this question.
I know in Heaven we do still retain our free will, but yet, no one will ever get thrown out of Heaven and there is no sin since we will be with God and sin will be impossible there. I know if a soul goes to purgatory they are assured of Heaven and also their free will still remains as well. Thus, if a soul still has free will in Purgatory how is it that they have free will yet still are assured of Heaven? I know in Heaven sin is impossible since we are with God, but in Purgatory it is my understanding that God doesn’t dwell directly with them and there will be much suffering? Thank you.
Free will doesn’t mean sin,; we don’t necessarily abuse our freedom just because we have it. In fact, purgatory is the very place where our wills are given the final touches, where our wills are further informed and molded and helped and so finally purified of the desire to sin, before entrance into heaven. Man’s will has always been both the problem and the “prize”, so to speak, that God wishes to orient rightly, without force. These teachings from the catechism continue to apply:
 Freedom is the power, rooted in reason and will, to act or not to act, to do this or that, and so to perform deliberate actions on one’s own responsibility. By free will one shapes one’s own life. Human freedom is a force for growth and maturity in truth and goodness; it attains its perfection when directed toward God, our beatitude.
 As long as freedom has not bound itself definitively to its ultimate good which is God, there is the possibility of choosing between good and evil , and thus of growing in perfection or of failing and sinning. This freedom characterizes properly human acts. It is the basis of praise or blame, merit or reproach.
sin is not possible in Purgatory, because there is neither the body nor the world, nor satan ,since sin comes through 3 ways as in 1 John 2:15 Do not love the world or the things in the world. The love of the Father is not in those who love the world; 16 for all that is in the world—the desire of the flesh, the desire of the eyes, the pride in riches—comes not from the Father but from the world. 17 And the world and its desire are passing away, but those who do the will of God live forever.
That is a very good question. But here is my opinion.
The souls in purgatory are in purgatory because before they departed this world they have already freely chosen to be with God. They just have to satisfy those temporal punishments due for their sins. For this reason, although they don’t enjoy the beatific vision yet, I think somehow that, before putting them in purgatory, God must have given them a glimpse or foretaste of what Heaven is like. In this way, and with other graces God gives them, they can persevere and endure the sufferings in purgatory.
Now, about the sufferings. According to St. Catherine of Genoa, there is a big difference between the souls in purgatory and the souls in hell. They both suffer, but the souls in hell suffer the terrible pain of loss, or the pain of having lost God forever. So they are angry and desperate. It is easy to imagine them forever hating God on account of their jealousy of those who are in Heaven. But the souls in purgatory are not desperate, nor hating God. They suffer the pain of not seeing God because they are yearning for Him whom their hearts desire (This is perhaps an effect of the glimpse they received before being put in Purgatory). They are longing for God and can’t wait to be with Him. Not being in Heaven is the source of their suffering. But the more they suffer, the more they repent of the sins they have committed. Their desire to be with God also make them realize the worthlessness of this world, and enable them to abandon their worldly desires. Thus, they are slowly purified of their attachment to creatures and now want nothing else but God. Purgatory, then, is more than a place of punishment; it is a place where God bathes imperfect souls with His tender mercy, making them worthy to enjoy His company in heaven. See St. Catherine of Genoa, The Treatise on Purgatory (This is a very short treatise, which you can read in one or two sittings.)
A soul is said to experience a longing for God that is so intense that it is intensely painful. This is why saints have sometimes said that a person can go to Purgatory not just for sins committed, but also for a lack of longing for Heaven and an over attachment to the lawful pleasures of the present world.
Holy souls in Purgatory have already been saved so they no longer commit sin. Only obstinate souls in hell continue to sin after death (hence why their punishment keeps extending on and on forever).
Yes, it is possible for those in Purgatory to sin. As you pointed out yourself, free will entails this possibility. This does not contradict the assurance of Heaven, because for those in Purgatory Heaven is only ultimately assured. That is to say, those in Purgatory will reach Heaven in the end, but while one is in Purgatory – and one may be in Purgatory for a very long time indeed – one is capable of committing further sins, and one would have to undergo further temporal punishment for those sins. The time one has to spend in Purgatory may therefore exceed the time needed to purify one of those sins accrued in this life.
It’s important to be aware of this. Many Catholics hold too rosy a picture of Purgatory. It is a place of suffering, possibly terrible suffering (if that is required to cleanse one of one’s sins), and there is no telling whether one will be in Purgatory a day, a decade, or a billion years. The only thing we can say with confidence is that in Purgatory one will not be bereft of God’s guidance. While that’s good to know, believers should still do what they can to avoid it or minimize their time there. Obviously the way to do that is to sin as little as possible, and submit as much as possible to temporal punishment in this world.
sometimes I get overwhelmed about all the evil and horrible and embarrassing things that I have done in my life and how all this will be revealed to every single person that has ever existed at the final judgement.
The silver lining is that first we experience the general judgement where will we receive our sentence.
So the silver lining is that if you go to heaven and even if you have to do some Purgatory time being embarrassed won’t be so bad.
Purgatory or as the East calls it Hades is interpreted as a ace or state of purification or waiting that is full of fire or darkness and gloom.
The difference between Purgatory and Heaven or Hell is that Purgatory or Hades the place of gloom is a temporary place or state of being of purification before Souls enter Heaven.
Purgatory or Hades will no longer exist after the final judgment in the end of time.