Stefan never consider taking the cure himself or giving it to someone else simply because he puts Elena above everything else.And not only his love for her but also the guilt he feels for her becoming a vampire.This season we saw him once again fighting with his inner self,with his consiousness,which is basically everything that makes his life miserable ever since he became a vampire.He felt responsible for Elena becoming a vampire and that meant a great deal to him.Yeah,of course,he wondered whether she'll come back to him or not if she takes the cure but mainly he was trying to find it so that he could help her become human again,so that she wouldn't go through the same stuff he did.He felt responsible for her and I think that's the main reason behind his actions.Of course he would go back to her in a heartbeat and those who say that his words in 4x23 were total BS are not right because no matter how hard he tries to move on he's still inlove with her and of course if he had the chance to have her he wouldn't lose it for the world.
Of course he needs to move on and accept things as they are,I agree about that.
As far as the shits that happened to him-well that's kinda what I expected for him this season.He kept a low profile in the whole season so that's why at the end we expected something to happen with his storyline.So yeah..it was shitty but it did happen.
Stefan made one big mistake from the begining-he would have never stayed in Mystic Falls cause that led to many things going wrong.But than again I can't really blame him cause he fell inlove and because he was feeling really lonely before coming back home.No brother,no love interest and carrying all the guilt in himself was killing him.So when he met Elena he found a purpose in his life again.Now he just have to face that things are not like they used to be anymore and he also has to deal with Silas,which will be a big problem for him.I guess that also when they show us a bigger picture of the history of the Salvatore family we'll find some answers about him and Damon and what their bond really means.So that will also probably give the answer to the question "what he did wrong".
Personally I don't think that he's really that wrong about anything.Yeah he makes mistakes but all of them do,he's not a horrible exception or something like that.He's not a treat to anyone and he just needs to stop reliving his life like he said in 4x18.