I realize all of that is a result of man doing it his way
rebelling against an all knowing God that warned us ahead of time.
Do you realize that is the question?

We are just as guilty as them because we don’t take God at His Word and for who He is.

Billions are doomed to eternal fire because they reject Him through their freewill.
Calvary is their chance and each/everyday they still reject it/Him accepting their justice, judgement, and punishment. That is what you call God’s righteousness, and holiness, and Him being just.

Why don’t you just slam physical death, it is simply another result of the same failure because we chose our way. God has left it in place post Calvary as well as the issues that you set forth.

Could God not have stopped it?
OH He did His part. HE warned them in advance and they chose their way. He gave them paradise and all but one simple tree.
Could He have stopped them, yes
But He would have denied His characteristic of freewill. That is just as much and real part of Himself as all of His other characteristics. Can God deny Himself – it is a question answered in your Bible.
All of your questions, answers, and theology that says otherwise is explained in the Bible also,
It says everyman is a liar, let God be true.
Romans 3:3-4
For what if some did not believe? shall their unbelief make the faith of God without effect? God forbid: yea, let God be true, but every man a liar; as it is written, That thou mightest be justified in thy sayings, and mightest overcome when thou art judged.

As far as God stopping it and them, the tree with the knowledge that would cause failure He placed it in the garden, and made it desirable to be looked at, taken, and eaten. Yet He left it up to them, personally.

Child cancer is a sad but true result of man’s rebellion.

Here is the question for you if you believe the God of the Bible as you say,
Where are the people with understanding of a God [(that stumbles through this human existence (as you present) since you understand him better than us]], that justly live by faith with healing in their beings (hands, prayers).

So why complain, ???
Do something about it.

Where are your gifts of the Spirit
One being gift(s) of healing…?

The guilt lays at the feet of the human race and the church that possesses (or should) the gifts of the Spirit – one being healing – not the gift of healing, but giftS of healing.

It seems you (project) and refuse humankind accountability.
Just as it happened in the beginning in the garden.

Happy healing
my Spirit filled brother.