Right, I read the fragment, and I can sort of see where AD got some of his ideas from, but he has clearly plucked some of the others out of nowhere.
The most obvious "change" is with Edward and Esther. Edward is presented as being a silly and foppish man, who pays a lot of attention to Charlotte in the initial part of the book. The conflict between them and Clara could be seen as coming from the situation with Lady Denham's inheritance, but there are certainly no open hostilities and I don't know where the hell AD got the thing about them only being step-siblings. I suppose it was so he could throw in the juicy incest bit, like he did with Helena and Anatole in his War and Peace adaptation. He seems to have a very unwholesome fondness for that sort of thing.
Sidney is barely seen but is spoken of fondly. I think if we assume that Austen intended for Charlotte to end up with someone, he is the most likely candidate, unless she was planning to introduce another character later on. But I think, unless I'm misremembering, that she usually introduced all the main players in the early chapters. It didn't say anything about Sidney being Miss Lambe's guardian either.
Sadly, there was no Mr Stringer or similar character. I suspect that it would be seen as a step too far for Charlotte to get together with a character who wasn't in the original text but who knows... enough liberties have been taken thus far so I suppose it's still possible!