I just don’t get the point of living a lifestyle that is anything short of Hedonism if everything is already written in stone.
I might as well drink to excess if it’s already been decreed.
I have no right to get upset if someone rapes a wife or two of mine because Yah already decided it was going to happen, so it’s not that that guy is really all that responsible.
In fact, why does He condemn me for lusting after a married woman if He already chose that path for me?
Those are great questions, in fact, you are exactly on track because your theology just came to the same intersection as Paul's:
"What shall we say then? Are we to continue in sin that grace may abound?"
Romans 6:1
The answer:
"By no means! How can we who died to sin still live in it?"
Romans 6:2
The answer to the rhetorical question in Romans 6:2 is that you can't live in sin if you are dead to it.
It's not that you might as well drink in excess if it’s already been decreed, but that you will drink in excess if it has been decreed.
"For I know that nothing good dwells in me, that is, in my flesh. For I have the desire to do what is right, but not the ability to carry it out. For I do not do the good I want, but the evil I do not want is what I keep on doing. Now if I do what I do not want, it is no longer I who do it, but sin that dwells within me.
...Thanks be to God through Jesus Christ our Lord! So then, I myself serve the law of God with my mind, but with my flesh I serve the law of sin."
Romans 7:18-20, 25
Here is the whole point of the knowledge of good and evil. This life is a lesson in contrast so that we can know what good is. Without evil we would never truly know good. God doesn't make the evil last forever, because once the lesson is learned, its purpose is complete. Therefore sin results in mortality. God has the power to justify all, because all comes from Him. Justification is simply God declaring that when you "messed up" such-and-such His purpose for it was really this or that. If your miss is declared a hit, how can there be condemnation against you? Putting Jesus on a cross looks like a huge failure, but it's not. If God declares Jesus a success in dieing, he will do so for you too.
In fact, why does He condemn me for lusting after a married woman if He already chose that path for me?
Does he condemn you? No. "There is therefore now no condemnation for those who are in Christ Jesus."
Romans 8:1
I have no right to get upset if someone rapes a wife or two of mine because Yah already decided it was going to happen, so it’s not that that guy is really all that responsible.
You would be right to be upset. Just because God creates evil does not make it good. Calling evil good is to miss the lesson of contrast. This hypothetical man is responsible in the relative, God is responsible in the absolute. The consequences he then faces in the relative (the law of the land, and possibly vengeance from you) will differ than the consequences he faces in the absolute (justification (yeah, grace seems unfair, be glad it is)). Both consequences, absolutely speaking, come from God. It's only confusing when we attempt to mix the things from the human perspective with the things absolute at the level of the Creator. The only reason it comes up is because God has allowed us to share his top-down view in several passages in the Bible.
When it comes to times of the end, partitioning what is revealed and from what perspective (ours vs. God's) will yield clarity.