So... these are excellent questions and I'm afraid I personally can't answer all of them since I'm not that knowledgeable here. But I do believe people smarter than I have come up with better answers than I will give too. I'm afraid I don't understand your question regarding original sin being forgiven. I'll try to answer the rest from my experiences, though

So think of it this way: if God created humans to have free will, this means they can choose to be bad. You may be asking, why would God create a world where bad can exist? Doesn't that seem flawed? But if God were to create a world where bad can't exist, then humans wouldn't have true free will. God didn't create the world with bad things in it, he created the world as good (in Genesis, the first chapter of the bible, he continually says "it is good" after everything he creates.)

So God creates the world as good and put humans with free will into the world. And because they have true free will, they also have the choice of making the world bad, which is what ended up happening. The pint is, "Bad" as a concept must exist in order for there to be true free will

So if bad can exist, then logically there has to be consequences for bad things. Otherwise it's not bad. If there are no consequences it can't be bad, it just doesn't make any sense. So sinning, which is the bad we've been talking about, has the consequence of death. I hope that kind of answers the question of "why do people have to be punished for sins"

Humans were not intended to be ignorant, and they were already intelligent. They just didn't have specific knowledge. And this is true even to this day. We as humans don't know everything and we never will. But humans had free will even before they had the knowledge from eating the fruit. They willingly disobeyed God's instructions before they even ate the fruit. They were already intelligent. I guess in a sense they were designed to be ignorant if by ignorant you mean "does not have unending knowledge about everything in existence". Then indeed, humans were never designed to have 100% of all the answers. If they did, they would be no different from God. And this is clear even to this day. Not even science can explain everything and we're always discovering/learning new things.

God didn't take anything out on Jesus, but Jesus sacrificed himself for other humans. I'm not sure of the imagery of hell, note that I could be wrong here , but Hell is separation from God, not necessarily a physical torturing session. And this makes sense, when you sin, you go further away from God since you're disobeying him. And when you disobey someone, that means you don't trust them. And if you don't trust them, you're not getting any closer to them. And hell is just eternal separation from God, which, to a Christian, is the worst thing you can experience if you truly believe God is the greatest gift and biggest form of love you can experience. That's kind of the gist of it

I couldn't answer your questions on humans in hell before crucification since I need to sleep now, but I do have some ideas/potential answers. I do think it is a question worth looking into, for both you and I!