How much of the influence to end the apartheid at South Africa was internal, how much was local, and how much was global?
I really don't know the answer to that. It's hard to say what kind of influence will work on the Israel apartheid, but a declared ongoing external war makes a strong impression that is an influence on the wrong direction.
I don't know that. Economic historians and others have to figure out exactly what caused the end of South Africa's apartheid system (my layman's guess is that it was a combination of multiple factors).
What I do know is that black South Africans begged us not to do business with their country until apartheid was abolished. Many of us (and even the US in the end) obliged and cut ties with South Africa. Palestinians are similarly begging us not to do business with Israel over similar human rights violations. We did (eventually) heed the black South Africans' call, so why can't we today heed the Palestinians' call?
Yes, most of them. The amount of land offered varied.
In particular check the Olmert peace offer from 2008 which offered Palestinians basically every single thing they wanted - but they refused it anyway (apparently because Abbas was too weak politically to make it happen, and Olmert did not want to go public without assurances from Abbas that it would actually happen).
(Not sure about the unconditional part though - why in the world would it be unconditional?)
Land provided with conditional use is not sovereign land. If the palestinians must continue to defer to israeli conditions on use then the land hasn't truly been returned.
The Olmert offering required the large settlements remain, which is an obvious non-starter.
I really don't know the answer to that. It's hard to say what kind of influence will work on the Israel apartheid, but a declared ongoing external war makes a strong impression that is an influence on the wrong direction.