1. it does contain sexual abuse of some kind. it was apparently by the father, harold. as for whether winston assaulted him in any way, im not sure.
2. i read that it does have a relatively happy ending, but not a very satisfactory one.
3. whatever misunderstanding is between them definitely gets cleared up but only about halfway through the story. but i don't think his name gets cleared among the family, or that they ever treat him with respect. and it seems like the ml follows the trope of hiding certain crucial things from eugene to 'protect' him which ofcourse always ends up leading to many problems.
what i found common in both the good ratings and the bad ones were that they were very frustrated by winston.