Didn't you say that God has predetermined our course of action? So when God gave Adam and Eve that command, had He already predetermined that they would disobey it? You did say that everything that happens is according to His will. So, was it His will for them to eat the fruit He had told them not to eat?
If He had predetermined their decision, then they really didn't have a choice in the matter, did they? So, in reality, when they disobeyed Him, they were doing what He intended that they should. It was His will for them to disobey Him.
Now, as you also said, as a result of this, we are all slaves to sin, right? So, since God set the whole thing up, and had predetermined the outcome, it was His will for us all to be slaves of sin.
So, again, if God has pre-chosen those who will obey Him, doesn't that imply that He has also pre-determined those who will not? And since, as you say, everything that happens is according to His will, doesn't it follow that it is His will for most of humanity to suffer in hell throughout eternity?