Well, thank you for actually posting a nice post.
I can see where you are coming from, particularly about the sin matter.
I just think that since we still exercise a will despite being predestined (we still willingly come if predestined or willingly don't come if not, etc.) that God is still just in making us pay for our actions. I know how some could disagree with this or see it as a stretch.
But, since I firmly believe the rest of the doctrine, I have to accept this as well because if I don't, it all falls apart. I don't fully understand it. I just believe it must be a mystery I fully won't know until I get to the other side. That is the thing about Calvinism. It is so tighly woven that if one part is wrong, it all pretty much has to be wrong as well.
I believe that as well. However, I don't accept it (Calvinism) due to the nature of predestination. I cannot believe God (who is the definition of "Good") would create people merely to throw them into Hell. Being created in His image we know the difference between Good and Evil. That act would not be Good. Thus He cannot do it.