From my understanding, this bit is a little off:
it seems that the idea was that basically the God of the Bible wanted to wipe out all of humanity as a result of them being such sinners. I’m not sure who thought up this plan, but Jesus came down to take the karmic burden upon himself.
The "God" in the old testament wanted to wipe out the people of the earth because of their evilness which was why he sent the flood and that whole thing with Noah and the arc. Again doesn't sound like a very loving God to me, and again you have to recognize that the Bible was collected by people who obviously weren't Jesus, so yeah that whole thing doesn't jive with me. That whole people are evil and need to be destroyed thing is all Old Testament. God of fear, jealousy, hate, envy, that sort of stuff.
The New Testament is about the God of Love. As far as Jesus coming down to "take away our sins" and "save" us, my current understanding isn't so much that we can just go out and sin and we aren't responsible anymore or anything like that. It's almost like, the mere fact that a fully realized being was here on earth, that the energy field left is so magnetic, that eventually no matter what, we have to be drawn back to it. That is what has "saved" us. As we are drawn to realizing that field for ourselves, our "sins" are automatically taken care of. Something like that.