I think first you need to get past the more elementary understanding of good and evil. For example your re-presentation of the Euthyphro dilemma (does God command actions because they are good or are actions good because God commands them?) is again a framework that doesn't produce a solution; the former undermines God by appealing to an external standard, and the latter becomes a tautology when we're trying to understand the goodness of God.
We can't assume a morally neutral framework, or even a naturalistic one. The former, because then we have no means to actually understand, the latter because different societies derive different ethics from "nature". We also can't appeal to pre-Christian understandings of good and bad because these were about qualities as opposed to actions - virtues were about excellence, not moral goodness, and this justified societal structures such as slavery.
If you want to take a Christian ethical framework (e.g., equality of worth of human life because it is human) that's fine, but then you also can't reject it out of hand without justification. You need to show why Christian ethics are superior or inferior or preferred to pre-Christian / pagan frameworks which find Christian ethics ridiculous.
Because you are a westerner you likely assume a Christian framework, broadly speaking. If we want to understand good and evil within that framework we should start with the axiom not of goodness but of evil. Evil itself IS the power of sin that humanity becomes enslaved to, which brings death and destruction and masters humans to their destruction. This is contrasted to goodness, which is justice, righteousness, order, life - and specifically flourishing life, good life, not just continued biological existence. But this is not sufficient in itself to describe God's goodness, because He is not limited to justice, or order as opposed to chaos, or flourishing as opposed to decay.
God has absolute freedom, and is not bound by necessity, or an external standard like justice, or even a teleological progression (i.e. God has no "aim" or "end-state"). This is why He is God, uncreated, unchanging. This is why He is distinct from both created beings like humans and even the claims of the pagan gods. We Christians understand that this freedom is part of Who and What He Is, His essential essence, which is beyond knowing or defining or categorization, being before and above and distinct from all created things.
His goodness becomes known to us by His actions, which we call His energies (from the Greek for work). These actions are part of Him, they are God, and they are eternal activities - loving, creating, healing, showing mercy, etc. They become known to us in time as we experience them. Good, then, is God's divine nature in action, a kind of vector sum of His energies.
For humans to be good, then, is for us to participate in those energies, and this is how humans are both healed of sin and flourish in life. Goodness and freedom come from this participation, because it frees us from the slavery to sin, chaos, death, and destruction.
This breaks the Euthyphro dilemma which is asking us to know whether things are good because God slaps the good label on them vs saying "He does good things so we call Him good". The problem is the Platonic mindset that expects goodness to be a form or abstract quality that requires an external reference point for meaning. Instead, God is personal and relational (a main difference between Platonic and Christian theology). We know God through His energies, and what we know from them is good because they bring life, order, flourishing. When we do good deeds, we're not copying what we call good, we are actively participating in God's eternal activities, and that goodness acts upon us. As opposed to picking between external standard and arbitrary divine will, here good is the eternal action of God Himself, made known through participation.
So - that being said - with good itself is so experienced and defined - I think you can see the challenge to Plato framework you're assuming here. God did not arbitrarily assume punishment. God's eternal actions are good, and life-giving, and being separated from them is chaos and separation from life: death itself. Death begins with physical death, and culminates in spiritual death.
The premise of coercion and torture you're assuming are not givens. Hell is not a masochistic torture pit. The image of hell - weeping and gnashing of teeth - is that of insanity, of loss of coherence of being. Loss of humanity, which is a loss of the image of God. If people are in hell, this hell is one of love, perceived as bad by those who hate Him - not because He wills them to suffer.
Your analogy of soldier and captive fail in the same way. This isn't a coercive tyrant setting arbitrary rules - the "rules" of love, righteousness, life, flourishing are God's eternal actions, His being in action. Rejecting this life and flourishing is not a choice between subjugation and punishment.
Similarly He is not subject to necessity. He is totally free. He is not bound to punish, reward, create in any way whatever. So while God could absolutely reprogram minds, what we know of God as revealed by His energies - which are again oriented to life, order, flourishing, mercy, love - would be contradicted by this type of manipulation or domination.
The hypothetical of sadistic torture being called good (back to Euthyphro) is already answered - such actions are not life-giving or coherent with the image of God the Father revealed perfectly in the person of Jesus Christ, who loves His enemies, forgives them, and dies to free them from death and slavery.
Free will is not as small of an idea as choosing between an arbitrary set of options. That's an objection I've seen here said, that humans aren't free because they can't fly - if so, only God is free, which is fine and true, but then we need to have another term to re-enter human experience. Instead freedom is the freedom to flourish, to grow toward our purpose, our teleological end. The call is not to pick between submission and torture, but to proceed toward what you were created for, life...a truly good, abundant, flourishing life. Not choosing your existence, or your sinfulness, or your need for salvation doesn't negate your free will even though it does negate you not being free like God is free. All you've established here is that You Are Not God.
Nevertheless your life, and mine, and all of ours, are gifts given to us for our salvation toward the best possible end any of us could imagine and more. Sin distorts this, and our sins are our participation in that distortion, not a "design flaw" from God. Salvation is our choice to participate in our own freedom. Humans are not passive victims of a divine game, but created with divinely-imaged agency, and are active participants who can choose to live... or to die. So the soldier analogy breaks down, because we're not talking about arbitrary penalties but intrinsic outcomes. If you refuse to eat you certainly will die. The person who tells you this is not the one who kills you, particularly if they continually offer you food.
A sadistic God calling torture good contradicts our knowledge of God's divine energies as life-giving, merciful, plenteous in mercy, longsuffering, compassionate, loving, and self-sacrificing - and so cannot be good, is incoherent with good. Your arguments are emotionally compelling, but ultimately come from a legalistic and Platonic view of Good and Justice that are not aligned with the theology and philosophy of the Church.
