First up - if you want to differentiate a specific section of text, keep it to a minimum - otherwise you end up with all sorts of weird formatting that makes it hard to read; if you are attempting to convince someone of the validity of your position through the argument you present, they need to be able to read it, preferably to be able to read it easily.
1. Even if God COULD have had many sons, if you accept the Christian view that he only had one, then that would make it significant. My personal view as an Ignostic, if the chidren of 'God' had great capabilities, then each would be important, though their individual importance would be diminished due to their numbers, a single one however is valuable due to its scarcity and this would make his involvement of greater importance.
2. A very good question; the traditional Christian view is that while in his phyisical form he was beset by suffering of the flesh and this seeped into his spirit such that he wondered if his father had discarded him. My personal view was that Jesus was not 'god' nor a son of god, so therefore he was speaking to his 'father in heaven', another way of referencing his god.
3. I agree, from a traditional christian perspective this is a problem; I believe one of the ways it has been traditionally met is that the original sin imprinted itself on us all so deeply, that it needed to be addressed with drastic measures, that humans had to be confronted by an event of significant divine impact. My personal view? Jesus was a guy who got crucified because his followers were making the local governors and their foreign overlords nervous.
4. The standard reply i have been given on this is that Jesus chose to do it himself.
5. Actually the word is 'gave' not sacrificed, though I understand the point. In which case the pat answer would be gave unto humanity or sacrificed upon the laws of humanity.
6. The traditional view would be that the sacrifice was the suffering; that Jesus sacrificed himself by undertaking pain and ultimately the feeling of death before regaining his true divinity. Personally I think it is not much of a sacrifice, but it sure would not have been pleasant.
7 + 8 + 9. I would suggest you read up on the idea of salvation through faith vs salvation through works, it is a lot more complex than you seem to think.
10. Where in the bible? But in any case, the original chrisitians were jews, therefore if you consider it from that perspective it makes sense that they were rather accommodating of their relatives and country men.
11. You should examine the concept of baptism of the spirit and so forth, as opposed to merely baptism of water or whatever it is called. The early church did agree that they went to hell, however later in the church's history they realised how screwed up that concept was.